Interview with Helen W. Dodson-Prince and E. Ruth Hedeman

Begin Tape 127B

Sullivan: 00:00

This is now talking with Helen Dodson Prince and -- what was your first name?

Hedeman: 00:08

Ruth Hedeman.

Sullivan: 00:09

-- and Ruth Hedeman at the IAU in Montreal on 20 August 1979. Well, first of all, can you tell me what your educational background was and when you first came into contact with radio astronomy?

Dodson Prince: 00:24

Surely. I was a member of the faculty of the University of Michigan, assigned to the McMath-Hulbert Observatory for research in solar studies. I was a member of the faculty of the university. I have a PhD degree.

Sullivan: 00:39

In astronomy?

Dodson Prince: 00:41

In astronomy. And I had been an optical solar astronomer since the mid-1930s, where I began my work at Meudon.

Sullivan: 00:52

Yes.

Dodson Prince: 00:53

Continued it at the Whitin Observatory at Wellesley College, where we had a spectrohelioscope. And then I was asked to join the staff of the McMath-Hulbert Observatory in 19-- well, I think it was '46, something like that.

Sullivan: 01:07

Right. And can I ask you Ms. Hedeman.

Hedeman: 01:09

I was a graduate student at the university after World War II came to an end. And then after I got my masters degree, I worked at the McMath-Hulbert Observatory for two summers as a graduate student. And then went out there after I got my masters degree and working full time after 1948, I think it was.

Sullivan: 01:30

Now, were you working under?

Hedeman: 01:32

And Helen and I have worked together there ever since.

Sullivan: 01:36

I see.

Dodson Prince: 01:36

Yes. We went to the same undergraduate college. We knew each other. We were friends. We both went to Goucher College in Baltimore.

Hedeman: 01:44

And we were both from [crosstalk] Baltimore, Maryland.

Sullivan: 01:47

Yes, I know that.

Hedeman: 01:48

Okay.

Sullivan: 01:49

But now so when did you first hear about radio astronomy?

Dodson Prince: 01:51

When I was in the Radiation Laboratory at MIT, and when I read that the radar equipment latched onto the Sun.

Sullivan: 01:58

Right. This was Hayes discoveries.

Dodson Prince: 02:01

Yes. And so I was highly --

Sullivan: 02:02

What kind of work were you doing at the Rad Lab?

Dodson Prince: 02:04

I was working in radar propagation.

Sullivan: 02:09

Theoretical work more or less.

Dodson Prince: 02:10

No plotting out.

Sullivan: 02:12

I mean, you weren't working with equipment is what I mean. Yeah.

Dodson Prince: 02:15

I wasn't working with equipment, no. I was in the patterns of the radar--

Sullivan: 02:20

The antenna patterns.

Dodson Prince: 02:21

The antenna patterns. And we provided them to-- we gave them to the generals.

Sullivan: 02:25

Right. So you heard about that the Sun gave off radio waves.

Dodson Prince: 02:29

Yes.

Sullivan: 02:31

And did this mean that when you went back to Michigan and began working on the Sun that you paid a special interest when these reports came in nature?

Dodson Prince: 02:38

Not at all.

Sullivan: 02:38

Not at all.

Dodson Prince: 02:39

No, not at all. It worked entirely differently from that.

Sullivan: 02:42

Okay, tell me.

Dodson Prince: 02:43

All right. You know that the radar equipment that worked on the Sun was in Australia.

Sullivan: 02:48

Yes.

Dodson Prince: 02:48

All right.

Sullivan: 02:50

Also in England, but in Australia first.

Dodson Prince: 02:52

Australia first. And Australia began, just tried to put together that which was observed in radio frequencies, and that which was observed on the Sun. But that which was observed in the Sun was observed primarily in European and U.S. longitude. So there was very, very poor cut across. And the first papers to try to put together optical and radio frequency studies were not really successful.

Sullivan: 03:24

They tried to work with Mount Stromlo a little bit.

Dodson Prince: 03:25

That's right.

Sullivan: 03:26

With C. W. Allen.

Dodson Prince: 03:27

That's right.

Sullivan: 03:28

Yes.

Dodson Prince: 03:28

And it was primarily because they really didn't have access to the good cut across data.

Sullivan: 03:35

By cut across, what do you mean?

Dodson Prince: 03:37

Time wise.

Sullivan: 03:38

Same time.

Dodson Prince: 03:39

When the Sun was up for one, it was down to the other. All right. Now, one of the-- the station in the United States, which according to my recollection began the radio astronomy program first was at Cornell.

Sullivan: 03:57

That's one of the first, yes.

Dodson Prince: 03:58

All right. And the person who was in charge of it at Cornell was Dr. Charles Burrows.

Sullivan: 04:03

Right. Do you happen to know where he is now or is he alive? Do you even know?

Dodson Prince: 04:06

I really don't know.

Sullivan: 04:07

He is one person I haven't been able to find.

Hedeman: 04:11

He retired a number of years ago and we've lost track up here.

Sullivan: 04:14

Yeah. I'm afraid I haven't [crosstalk].

Dodson Prince: 04:15

No. He knew me at the Radiation Laboratory. He was connected with the Radiation Laboratory at MIT where I was during World War II. And he knew that I had gone to the McMath-Hulbert Observatory as a solar astronomer. And he had collected at Cornell a large assemblage of 200 megahertz solar records. And it was very difficult to know what they meant.

Sullivan: 04:52

What to do with it all.

Dodson Prince: 04:53

So he wrote to Dr. McMath and asked if he could have the privilege of asking us to assist him in the interpretation of the records. The request came from Dr. Burrows.

Sullivan: 05:04

But took the initiative, then, but he wrote there because he had known you.

Dodson Prince: 05:09

Yeah. He knew me. And he knew it was a solar station, but he also knew me.

Sullivan: 05:12

And what year was this now?

Dodson Prince: 05:13

Oh, heavens. I'm going to say '48.

Hedeman: 05:15

Somewhere in the late 1940s.

Dodson Prince: 05:18

'48. '47. '48.

Hedeman: 05:20

But the late 1940s. I wouldn't [crosstalk].

Dodson Prince: 05:22

It was '46, '47, '48. I can't produce the date.

Sullivan: 05:26

Your first paper was '49, so I guess it was before then.

Dodson Prince: 05:29

Oh, it was before then if that was my first paper. What was that first paper called? Do you have it?

Sullivan: 05:35

Well, I don't have the title. It was in APJ and it was about the May '49 flare, which was observed by Shapley and Davis in the radio. Now were they from Cornell? I wasn't sure about that.

Dodson Prince: 05:44

No. No. No.

Sullivan: 05:45

No. They were at NBS, I believe.

Dodson Prince: 05:46

But we give the radio frequency emission with that [crosstalk].

Sullivan: 05:49

Right. I think they were at NBS, actually.

Dodson Prince: 05:51

Yes.

Hedeman: 05:51

What is the date of the first paper about the 200 mega-cycle? A meter wavelength associated--

Sullivan: 05:56

That's '51.

Dodson Prince: 05:58

So but that--

Hedeman: 05:59

Now, I was at the observatory when Dr. Burrows came, so it would have had to have been either '48 or '49 that he came. Somewhere around there.

Sullivan: 06:08

Yeah. '51 is the first time you start talking about 200 megahertz. But now why did you take a special interest in this?

Dodson Prince: 06:15

Because it was new.

Hedeman: 06:18

And it was a challenge.

Dodson Prince: 06:18

And it was--

Hedeman: 06:20

We tried to pin it down to solar events.

Dodson Prince: 06:23

All right. Now, Dr. Burrows brought with him what he thought were the most important events at 200 megahertz and presented us with these great events on his records. All right? And we took those records and went to the Sun and came up with a very disappointing story. Sun wasn't doing anything much that you could say. It was active. I mean, there were centers of activity, but the time associations were far from good. What he was really presenting us with the onsets of noise storms.

Sullivan: 07:02

As it turned out later. But you didn't recognize it then yourself.

Dodson Prince: 07:04

Of course, we knew it then. Of course, we knew a noise storm when we saw it. We weren't that dumb. But the Sun wasn't telling the story. So we said, "Let us turn the tables." You see, he presented us with radio frequency events. And we said, "Let us present you with solar events and see what your record says when there is a solar event." Now, we were in a particularly good position to do this. The most active solar phenomenon is a solar flare. And we had just prepared photometric light curves, which give excellent time data of start, maximum, and end. I mean, it has the full light curve.

Sullivan: 07:50

It's just like the stripdrive record in the radio, right?

Dodson Prince: 07:52

Yes.

Sullivan: 07:53

Except [crosstalk] flares.

Dodson Prince: 07:54

Except that it has to be derived by many more hours of human labor we had photometric light curves for 100 flares. And mainly during the same observing hours.

Sullivan: 08:10

Yeah. So you have a good overlap.

Dodson Prince: 08:12

Yeah. So we have a good overlap. And we proceeded on the exploratory investigation to see what would come out of it.

Sullivan: 08:26

Correlated with what?

Dodson Prince: 08:26

Now, in all of our working in radio astronomy, we always asked to have a colleague who was a specialist in the field. We were not radio astronomers, so we asked that we have a colleague to work with us and Leif Owren. Have you interviewed him? [crosstalk] Leif Owren became our colleague in these matters.

Sullivan: 08:52

What was his background?

Dodson Prince: 08:54

He was in Norwegian.

Hedeman: 08:57

He was over here at that time.

Dodson Prince: 08:59

At Cornell.

Hedeman: 08:59

At Cornell.

Sullivan: 09:00

So he was--

Hedeman: 09:01

Working with radio.

Dodson Prince: 09:04

I didn't know that he was a graduate student. He may have been a staff member.

Sullivan: 09:09

So did he come to Michigan often then?

Dodson Prince: 09:11

Yes, he would bring records and we--

Hedeman: 09:16

We would go over them together, and you remember they then set up a machine that would duplicate their record.

Dodson Prince: 09:26

Yes. And so as they were obtained records, they made duplicate records for us. Now, the main thing that came out of the first study was that the 200 megahertz phenomena at the time of flares had a very complex time pattern separated on either side of the maximum of the flare. There were the early events, and there were the late ones. If you looked, have you looked at our paper?

Sullivan: 09:59

I looked at all the abstracts. I haven't looked at the actual papers, but I get the impression that there were two main kinds of events, like you say, either the max burst or the slow rise.

Dodson Prince: 10:09

We organized them according to this time relationship. There were phenomena that had early bursst and a late burst, and there were flares that had only early bursts, and there were flares that had only late bursts and there were flares that hadn't either.

Sullivan: 10:36

Right. But most of them it seemed had radio bursts. Is that correct?

Hedeman: 10:40

Most flares?

Dodson Prince: 10:41

Most of the flares had something, but--

Sullivan: 10:44

But not necessarily a burst, it could be just a little indication of a little arms or something?

Dodson Prince: 10:48

For the late phenomena--

Sullivan: 10:50

80% of flares have 200 megahertz activity. That was one paper you had.

Dodson Prince: 10:58

The late phenomena merged into the [unexpected?] of noise storms. So that the very late time, this showed why it was so difficult when you were given a noise storm to try to find out what the Sun was doing. That was so late after a flare you're not recognized. So that the Australian papers and our first exploratory effort--

Sullivan: 11:21

I see what you're saying. That's why they didn't show much correlation?

Dodson Prince: 11:24

Yeah, it's because of this time problem. And it was the orderly presentation, I would appreciate it if you would look at the paper because it's very clearly shown in the paper.

Sullivan: 11:38

The patterns that were--

Dodson Prince: 11:40

The patterns that came out. And I cannot emphasize strongly enough. The reason we were able to do that was that we had clean flare data. We had reliable and clean flare data.

Sullivan: 11:52

What exactly do you mean by clean?

Dodson Prince: 11:53

I mean, the time of start was known to the nearest minute.

Sullivan: 11:58

So a very persistent monitoring-

Dodson Prince: 12:01

if you take the flare data just from the reported, the reports of flares, in those days, you did not get--

Sullivan: 12:07

It was too sloppy, and it's the quarters, and-

Dodson Prince: 12:09

It was too sparse. It was too sparse. And it was very important to know the time of maximum, and this is something that is very poorly known even today, unless you have photometric light curves, and most people don't have photometric light curves.

Sullivan: 12:27

Looks like you say, it's an awful lot of work.

Dodson Prince: 12:28

It's an awful lot of work. And the coming together of the availability of those photometric light curves and the search of the radio frequency data was a happy circumstance. Don't you agree with--?

Hedeman: 12:43

Mm-hmm.

Sullivan: 12:44

Now how much were you inspired to change your program at McMath because of this radio data? Did it mean that you did different things when you monitored the Sun, or what have you done? Were you just using the data in a different manner, the optical data?

Dodson Prince: 12:56

We kept right on in the same way.

Sullivan: 12:58

The same? I see.

Dodson Prince: 12:58

That's right. No, it did not--

Sullivan: 13:02

It didn't influence what you did.

Dodson Prince: 13:02

No, it didn't. No.

Sullivan: 13:04

Right. And do you think it influenced the radio people as to what they did? Did they begin learning more about the proper way to go about doing the monitoring, or was it pretty much the just keep a [inaudible]?

Hedeman: 13:14

I don't--

Dodson Prince: 13:15

I don't think so. It was, [I don’t think?] we understood what was going on.

Sullivan: 13:24

Did you visit the radio observatory's office?

Dodson Prince: 13:26

We didn't go to Cornell.

Sullivan: 13:28

Did you go to the--?

Dodson Prince: 13:29

Did he go--

Hedeman: 13:30

We did. Dr. Burrows invited us once. We went there to Cornell.

Sullivan: 13:34

But you did this at Covington's?

Hedeman: 13:36

We stayed with the Burrows. And well, now we must go on to tell you about our association with centimeter wave.

Dodson Prince: 13:47

Yes. You see, this was 200 megahertz. Then there are other radio frequencies which could be [different?]. So we got in touch with Covington, so.

Sullivan: 13:58

Right. It was very narrow geographically also.

Dodson Prince: 14:01

Yes. And one very cold winter.

Hedeman: 14:06

January of 1955. '53.

Dodson Prince: 14:10

Was it '53?

Hedeman: 14:11

Yeah.

Dodson Prince: 14:12

Was it '53?

Sullivan: 14:13

The first paper you had with Covington is ‘53.

Dodson Prince: 14:16

So it was ‘52 or ’53.  Our mugs-?

Hedeman: 14:18

Yeah. It was January of '53 that we went out there.

Dodson Prince: 14:22

We took our photometric-- I mean, the dates on-  When we were up there was Covington, we acquired some Coronation mugs. And I didn't think the Coronation had taken--

Sullivan: 14:32

It was '53?

Dodson Prince: 14:33

That was '53.

Sullivan: 14:34

Or '52. One or the other.

Dodson Prince: 14:35

I think don't they say '52?

Hedeman: 14:37

I thought the mugs said '53. That's why I hitched on the '53.

Sullivan: 14:41

No, it was’ 53 because she had her 25th-year thing last year.

Dodson Prince: 14:44

Okay. Yes, it was '53. So yeah, they [inaudible] '52.

Hedeman: 14:48

But it was cold January.

Dodson Prince: 14:51

It was cold in January.

Hedeman: 14:51

And we--

Sullivan: 14:52

So--

Hedeman: 14:53

We visited him.

Hedeman: 14:55

And so Covington did not, when we went there, he was not aware of the flare association with his numerous events. He was aware that during some flares, there was enhancement of 2800 megahertz, but he had no realization that it was a very close rapport.

Sullivan: 15:13

He had never made any efforts to really get some optical data, right?

Dodson Prince: 15:16

He did during an eclipse but-- But not on a day to day.

Sullivan: 15:22

He hadn't been going for six or seven years.

Dodson Prince: 15:23

Well, yes, but he didn't have access to the flare data. I mean, that was not his obligation. So we made ourselves available to him as our--

Sullivan: 15:35

Why were you particularly interested in the higher frequencies. Just out of curiosity?

Dodson Prince: 15:38

No, just because the field should-- you should not limit yourself just to meet a wavelength. If centimeter wavelengths also exist, the pattern could be the same or different.

Sullivan: 15:47

Right. But I was particularly curious about seeing what was going on deeper down in the Sun where the centimeter waves originate, or is it just something different?

Hedeman: 15:54

At that time, not much else existed, you know, besides what Cornell was doing and what Covington was doing.

Sullivan: 16:00

True. Well, that would be easily accessible to you anyway.

Dodson Prince: 16:03

It was.

End tape 127B, Begin tape 128A

Sullivan: 00:01

Okay. This is continuing with Helen Dodson-Prince and Ruth Hedeman at Montreal on 20 August 1979. Now we were at the point about you had gone up and seen Covington’s data. He gave you his data. What things did you find about the centimeter waves?

Dodson Prince: 00:17

It was much easier to--

Sullivan: 00:19

Why is that?

Dodson Prince: 00:19

--because of the lack of the counterpart of noise storms and type I bursts floating around and type III bursts. The phenomena were primarily flare associated so that when you saw-- it was isolated.

Sullivan: 00:42

Right. I see.

Dodson Prince: 00:42

All right. And having had the experience of organizing the 200 megahertz data into early and late phenomena, we recognized the same thing in the 10 centimeter data.

Sullivan: 00:57

Pretty much exactly the same sort of thing?

Dodson Prince: 00:59

No. It isn't exactly the same sort of thing because there was never-- the occurrence of events that began long after flare maximum, the wave, there were 200 megahertz. There was a much tighter time relationship, wouldn't you say, Ruth?

Hedeman: 01:19

Yeah.

Dodson Prince: 01:20

And practically, there were a few flares that didn't have 2,800 megahertz, have something at 2,800 megahertz, but very few. They were very inconspicuous flares, but again, you had the same pattern. Some had an early burst. Some had a late response. Some had both early and late. And some few had nothing. So that it was a gratifying pattern that was emerging that essentially, the flare pattern could be recognized at the two frequencies, although the records looked very different and so forth.

Sullivan: 02:04

Did you ever do a study where you looked at both radio frequencies for the same set of flares?

Dodson Prince: 02:09

Absolutely. If you will look at our publications, you will find these.

Sullivan: 02:12

I didn't remember seeing it in the abstracts, anyway, the mention of that. Did that reveal any new aspects, or?

Dodson Prince: 02:18

No.

Sullivan: 02:19

No, [technically?]?

Dodson Prince: 02:19

No. They look very different because of the types of recording. But you will find that they are brought together in the articles. We took great pride in doing this because we did have the two records.

Sullivan: 02:36

Another question is with the 10 centimeter data, it was the first time, I believe, that you mentioned that you see some difference between when a flare is on the limb and when it's on the central meridian in the occurrence, indicating some non- [crosstalk].

Dodson Prince: 02:53

The second part is much stronger for flares near the central part of the dish than for flares near the limb.

Sullivan: 02:59

The second type of flare, you mean?

Dodson Prince: 03:01

Yes. The flares with the post-maximum burst at 2,800 megahertz, to us, seem to be greater when the flare was closer to the central meridian than when it was closer to the limb.

Sullivan: 03:13

And did you take this to indicate that the radio emission was directed in some fashion, or?

Dodson Prince: 03:17

We left that to the radio astronomers.

Sullivan: 03:18

I see. So you never yourself got involved in the physics of the flares

Dodson Prince: 03:21

We never take it-- no. Not in the--

Hedeman: 03:24

We left that to our radio astronomy colleagues. We were doing the optical flare.

Dodson Prince: 03:29

The what was going on in the Sun. All right? Then we come to something that is not reflected in your set of--?

Sullivan: 03:38

Yes. This is only radio-related things.

Dodson Prince: 03:40

This is the only radio related is what I'm talking about. Now, we had done 2,800 megahertz flux, 200 megahertz flux, but the other source of solar information was 80 megahertz, in Cambridge in England.

Sullivan: 03:57

Oh, yes. I didn't get that.

Dodson Prince: 03:58

I know, because we haven't published anything

Sullivan: 04:01

Well, if you didn't publish it, how am I going to know about it?  [laughter]

Dodson Prince: 04:03

We're telling you about it.

Sullivan: 04:04

Right. That's why I'm doing these.

Dodson Prince: 04:07

That cover--

Sullivan: 04:07

What year is this now you're talking about range?

Dodson Prince: 04:09

'55.

Hedeman: 04:09

1955.

Dodson Prince: 04:09

1955.

Sullivan: 04:11

So you wanted to go to get a lower frequency to cover that.

Dodson Prince: 04:12

We wanted to get a lower frequency. We wanted to cover the range and so we got in touch with Ryle and Hewish and they were good enough to say, "Come over to the Cavendish." And so in the summer of 55, Ruth and I went over and we were tucked up in the attic of the Cavendish Laboratory. And they brought out all of their records and we brought out all of our--

Hedeman: 04:37

Flare lists.

Dodson Prince: 04:38

--flare lists and light curves and found that there was nothing too different. I mean, the pattern--

Sullivan: 04:48

From 200--

Dodson Prince: 04:49

From 200 megahertz. There was a tendency to emphasize the noise storm aspect. Their record-- let me see. It had an interferometer.

Hedeman: 05:05

Yes. [crosstalk] interferometer record [crosstalk] take that into account.

Sullivan: 05:07

It had the fringes.

Dodson Prince: 05:08

Yes. So that it was-- and we did not have a radio astronomer as a colleague. We had to plow through it ourselves. And we plowed through it enough to know that nothing was too different, so that we did not pursue it to the point of a publication.

Sullivan: 05:27

I see. And you didn't feel it was worthwhile to publish [crosstalk].

Dodson Prince: 05:30

That's right. I mean, it was an enjoyable summer's experience, but it wasn't something that we felt we needed to do anything. We were busy doing other things.

Sullivan: 05:45

But why is it that-- I mean, there were many other solar optical astronomers at this time, and I don't know of any others that were as interested as you in correlating with radio emission. There were some that had some interest, but nobody had this long sustained interest. Do you have any idea why there was this attitude or?

Dodson Prince: 06:04

No. I have no idea why they weren't as interested in it as we were. It was the new thing, and we were interested. Maybe it's because new things were thought of-- I think McMath [crosstalk].

Sullivan: 06:16

Or do you have an idea?

Hedeman: 06:17

No. But you are aware-- are you not, in the publication called the Quarterly Bulletin of the Solar Activities that they started publishing the--?

Sullivan: 06:27

In the late '40s. That's true. Steve Smerd, of course, was very much involved in that. So that definitely indicated activity but not to the extent of actually doing deep studies such as you both did.

Hedeman: 06:42

Maybe it was just a matter of personality. We enjoyed what we were doing. There was a certain satisfaction about finding something going on on the Sun that went with the radio events. We enjoyed making that association.

Sullivan: 06:56

Also, apparently--

Dodson Prince: 06:57

We were also interested in searching for something that would differentiate between flares that were geophysically effective in causing geomagnetic disturbances and those that were not.

Sullivan: 07:08

Right. You got into that in the late '50s, it looks like, where you talked about the crochet-flares and the geomagnetic indices. Oh, did you find any good indicators up through the early '60s now, not going into later history?

Dodson Prince: 07:25

We published something on major early bursts. This was before the identification of type IV emission. And we had tried to associate type IIs. We had difficulties. Type IIs tended to be, so that we didn't know what the major early bursts were. I'm not sure that I know now what they really were. Everybody wants to say that they were type II bursts. Maybe they were. We'll never know.

Sullivan: 08:14

I see. These were these things that correlated with the SC magnetic storms--

Dodson Prince: 08:21

Yes, yes, yes.

Sullivan: 08:22

--a couple days later.

Dodson Prince: 08:23

Flares with only late-type phenomena did not seem to be as effective. Am I not remembering correctly?

Hedeman: 08:35

I don't remember.

Sullivan: 08:37

I can check the papers on that, of course.

Dodson Prince: 08:41

What has really evolved, in later years, which you probably don't realize, is that we have evolved what is known as the comprehensive flare index. Have you ever heard of it?

Sullivan: 08:58

I've heard the name, actually.

Dodson Prince: 09:00

All right.

Sullivan: 09:02

Really, really [crosstalk].

Dodson Prince: 09:02

And you're familiar with the evaluation of flares, importance 1, 2, and 3, which is the H-alpha flare. You are aware of all of the radio frequency things that go with flares. Now, we have evolved that which we call the comprehensive flare index, which is based on five components.

Sullivan: 09:24

Indicators of [crosstalk].

Dodson Prince: 09:25

Five indicators. The ionizing radiation, which is-- if you are observing and can get it, there's the X-radiation. If not, you take what it does to the Earth's ionosphere, and you evaluate it on a scale of 1 to--

Hedeman: 09:39

3.

Dodson Prince: 09:39

--1 to 3. The H-alpha, the optical observation, on a scale of 1 to 3. The 10-centimeter flux on a scale of--

Hedeman: 09:50

The logarithm.

Dodson Prince: 09:50

--of the logarithm of the-- logarithm of the flux.

Hedeman: 09:56

The dynamic spectrum.

Dodson Prince: 09:57

The dynamic spectrum.

Hedeman: 10:00

Emphasizing the type II and type IV by calling the type IV a III and the type II a I and continuum, kind of in between, we evaluated that as II. So each one of these, we tried to have a I, II, III--

Dodson Prince: 10:15

Then the last is meter wavelength radiation. And what we have found is that the flares that are great in all of these aspects are great in their geophysical aspects, and the flares that are missing in either one or the other, they sometimes miss in the geophysical aspects.

Sullivan: 10:43

Now, when was this developed? Now, what year?

Dodson Prince: 10:46

It's published as a UAG bulletin, number 14.

Sullivan: 10:52

What year?

Dodson Prince: 10:53

Oh, '60s.

Sullivan: 10:54

[crosstalk] [look like?]?

Hedeman: 10:56

Sometime in the '60s. We actually started compiling this index for our own use of the observatory years before that. And then--

Sullivan: 11:05

Once you had some confidence [crosstalk], right.

Hedeman: 11:07

--NOAA asked us to submit it for a publication. And the first publication covered the years from 1955 to 1969.

Dodson Prince: 11:19

1969, I think.

Hedeman: 11:20

Yeah, yeah.

Sullivan: 11:23

So the basic details of your index were first published in the late '60s, then? Because I'm trying to--

Dodson Prince: 11:30

I'm--

Hedeman: 11:31

It's somewhere in the '60s. I don't remember the exact date.

Dodson Prince: 11:32

Or were they published in the '70s, Ruth? Maybe they were published in--

Hedeman: 11:36

I don't know. I don't remember the year.

Sullivan: 11:38

Well, I can check that also.

Dodson Prince: 11:39

It's--

Hedeman: 11:39

It's UAG 14.

Dodson Prince: 11:40

--UAG.

Sullivan: 11:40

That's somewhat after my study is ending. It's interesting to know that this is what it will lead up to.

Dodson Prince: 11:43

But I mean that-- I mean, you asked us about--

Hedeman: 11:45

This grew out of our interest in the--

Sullivan: 11:47

Sure, this was all--

Hedeman: 11:48

--combined radio astronomy data as well as the--

Sullivan: 11:51

This is all a precursor to the [crosstalk].

Dodson Prince: 11:52

Yes.

Hedeman: 11:52

Yes.

Dodson Prince: 11:53

And we use this comprehensive flare index in our later work in evaluating the high energy, the solar sources of the high-energy events in the neighborhood of the Earth. We also have a second UAG publication with this comprehensive flare index, which gives it for the later years. I mean, there are two of them in case you get mixed up in it.

Sullivan: 12:20

Now once again, confining ourselves to before 1960, are there any other major points about your work relative to radio solar activity that we haven't covered? I see that you correlated, for instance, a 10-centimeter daily flux with calcium plage area and some other things like that. But I guess these were side things that you were doing.

Hedeman: 12:43

There was that interesting paper that you and Covington published together after the big flares in May 1951 when he had an absorption affecting his record. And he showed that it was-- we had a beautiful optical record to go with it.

Sullivan: 13:04

Which showed what?

Dodson Prince: 13:05

Oh, right. That showed that there was an ejection on the Sun and it came out and covered the flare.

Sullivan: 13:15

Oh, I see. And then that presumably was what absorbed the radio waves.

Dodson Prince: 13:19

That's right. And that is published. That's one of the things that we published.

Sullivan: 13:26

Another question is that most of the time you were dealing with low angular resolution data so that one only had the total radio flux from the Sun. The only time that I've seen that you got involved with interferometric data is in this '52 paper where you had the Cornell interferometer and you correlated some positions in the radio with the optical.

Hedeman: 13:51

I think that was at Covington's request too.

Dodson Prince: 13:52

Yes.

Sullivan: 13:54

It would seem to me that that would be sort of an important thing to do, to follow this up some more. But you--

Dodson Prince: 14:01

We used primarily time associations. We were moving away from this when the high-resolution position work moved in. Others were.

Sullivan: 14:15

You were moving away from-- you mean when the Culgoora came along and so forth.

Dodson Prince: 14:18

Yeah. I mean, the association with what the Sun was doing had been taken over by others. I mean, the question that you asked in the beginning, "why didn't others?" Well, now others began to come into the field.

Sullivan: 14:33

In the '60s. Yeah.

Dodson Prince: 14:33

We had been the pioneers. And so we were happy and content to let others who were closer to the radio astronomers than we were. We've always felt that you needed to have an expert in the associated field if you were going to do something in the field. Don't meddle in what you don't know.

Sullivan: 14:58

Well, the only other thing I think I would ask you is what do you think is the main thing that radio astronomy, or the main things, that radio astronomy has told us about the Sun? Once again, confining ourselves to pre-1960. Did it really show us a new Sun, or was it really only an extension of what we had known from optical work?

Dodson Prince: 15:19

Well, it let us have information about what was going on in the corona of the Sun to which we had no access prior to the radio astronomy days, except at times of eclipse and so forth, which were rare indeed. So it opened up a whole new avenue of phenomena. It was adding a new right hand. Yes without it, we'd hardly know how to get along. We haven't had to study the Sun without the benefit of radio frequency data.

Sullivan: 15:59

That's true. Well, when you first started, you didn't have it anyway.

Dodson Prince: 16:03

When we first started. But I mean, it really wasn't until after World War II that at least Ruth and I began working together. And by that time, it was one of the first things that we did, was to get involved in the radio frequency data. And we always had access to it from then on out.

Sullivan: 16:25

Right. I see what you mean. Okay, well, thank you very much.

Dodson Prince: 16:28

All right. It was our pleasure.

Sullivan: 16:32

That ends the interview with Helen Dodson Prince and a little bit of Ruth Hedeman also in there, at Montreal in the IAU, 20 August 1979.