Robert Winglee, Space Sciences Editor
American Geophysical Union
2000 Florida Avenue, N.W.
Washington, D.C. 20009
Telephone(202)462-6910 ext.326
Fax (202)462-2253
Editor's Assistant:

December 29, 1997

Dr. Robert B. Sheldon
Center for Space Physics
Boston University
725 Commonwealth Ave
Boston, MA 02215

Re: "On the physical origin of outer radiation belt 1-10 MeV electrons"

Dear Dr. Sheldon:

We have sent your paper back to the orginal two referees for evaluation. As you will remember from my previous letter dated October 6, 1997, I had indicated that both referees found that the data were very interesting but that they had major concerns about the discussion section on the cusp acceleration process and it was these concerns that were holding up publication of your paper.

Thier re-reviews of the manuscript indicate that the above concerns have not been eliminated. As a result, I cannot consider your manuscript further for publication in Geophysical Review Letters.

I am enclosing the referees' reports, which you may find helpful if you decide to revise your paper and submit it to another journal. I am sorry that I cannot be more encouraging at this time.

Thank you for your interest in Geophysical Review Letters.

for Robert Winglee
Space Sciences Editor

via Maura T. C. Wright
Editor's Assistant

Referee A

Please find enclosed a review of MS# 6091-rev2 "On the physical origin of outer radiation belt 1-10 MeV electrons" by Sheldon et al. This is my third review of this manuscript. Although the style and tone of the manuscript has improved significantly from the original version, the discussion of their proposed mechanism for populating the outer radiation belt remains speculative. I still do not feel comfortable recommending the manuscript for publication in Geophysical Review Letters. I rarely encounter a manuscript that I have major reservations about after one or two revisions. Since there has been little change between revision 1 and revision 2, I do not think it is necessary for me to review future manuscripts again. I had very few additional comments on this version. Please do not send the manuscript back to me again. The decision to publish the paper is, of course, yours.

Review of "On the Physical Origin and Prediction of Killer Electron Storms" by R. B. Sheldon et al.

Although the author has changed the title of the section A Theory of Cusp Acceleration to Discussion, the content of the section is nearly unchanged. This section is basically a discussion of a proposed mechanism and is still speculative. The author in his reply to the second review says that his goal is to show that the speculation is observationally consistent. If so, he needs also to address comment #1 below. Even with reply to the comments below, I am uncomfortable about recommending this manuscript for publication in GRL.

New Comments:
1. From the observations it was found that the intense cusp fluxes observed on Oct 14 were preceded by 35 hours an enhancement seen in the radiation belts on Oct 16. Is this time scale consistent with the diffusion time from after electrons would have been escaped the cusp trap in the Sheldon's proposed theory?

2. The tick marks and labels for L should be included on at least one of the panels of Figure 2. I suggest showing them on the bottom panels. Without tick marks and labels it was difficult to follow the discussion of this figure. There also should be mention that the white labels in the panels correspond to day of October 1996.

3. Pitch angle is misspelled in the text.

Referee B

Report to Authors

Dear Dr. Winglee

Again I regret rejecting this paper. The detection of trapped electrons in the cusp is a notable finding and deserves publication in GRL. However, in my view the interpretation is so faulty and shallow, this paper should not be published. If the authors would limit the paper to the experimental results, I would support publication in spite of the conversational style which lacks precision.

In the first version I objected to the vaguely described acceleration mechanism. In the second version this section was clarified enough to convince me the mechanism was incorrect. In this last version the same problem exists in the first paragraph of the Discussion. One simply cannot accelerate particles repeatedly by passing them in closed paths in a DC electric field. The field is conservative.

This third version still seems too long, philosophical and rambling. Some new ideas are put forward, but the theoretical backup, with the exception of particle tracing in the cusp, is lacking. The authors should concentrate on the experimental part and justification thereof, which would make a good GRL paper. The Discussion adds nothing but makes one suspicious.

As this is my third look at the paper, I feel the authors and I are not converging. Perhaps it needs a fresh look by another referee.

Message to Authors

The style is too casual, philosophical, and vague to inspire confidence in the important result presented. However, if the authors insist on this approach, I would not object. The primary problem is with the Discussion section which still has too much speculation, questionable processes, and unsubstantiated statements. Comments, mostly minor except for page 8, are given in the order in which the items appear.

p.3 line 7, Van Allen (1959) is not in reference list. (Actually you may have too much history for a GR Letter. (Van Allen, Stormer, Fermi) i.e. you don't reference Thompson when you mention electrons.)

Fig 2. Range in L and Energy should be given on at least one section. I gather from Fig 1 that Energy goes from 515keV to 8820 keV, but L appears to extend to lower values than in Figure 1.

p. 6 I found the correlation between cusp and trapped electrons unconvincing in Figure 2. A more quantitative presentation than these color figures is needed. Also, in view of the large variations in both cusp and outer belt electrons, cannot an argument be made that the outer belt is the source of the cusp electrons?

p8 First paragraph of discussion. I believe the repeated gains in energy by recirculating in a DC electric field cannot occur. The particle will gain kinetic energy as it falls through the electric potential and lose an idential amount of kinetic energy as it climbs back up to the starting point. The scattering and magnetic deflections do not change energy. How can the particle "drift without scattering, returning to its orginal position" without losing all the kinetic energy it acquired in the first crossing of the cusp? This point is fundamental to the interpretation part of the paper.

p10 Even if 5 keV electrons had the same rigidity as 500 keV Oxygen ions, (which they do not) they will not follow the same trajectories since they grad B and curvature B drift in opposite directions and will therefore experience different E fields.

p10 Even if the cusp trap has higher f than the dipole trap, diffusion into the dipole is only allowed if a mechanism exists.