Dear Dr. Pu, Thank you very much for your Decision Letter. I ...

Dear Dr. Pu,
Thank you very much for your Decision Letter.
I prepared replies to both Reviewers and slightly changed the text of manuscript
(marked by bold font).
Sincerely yours,
Yuri Yermolaev
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From: jgr-spacephysics@agu.org
To: yermol@iki.rssi.ru
Date: Tuesday, March 4, 2008, 6:11:27 AM
Subject: 2008JA013040 (Editor - Zuyin Pu): Decision Letter
Files: Ñîîáùåíèå.html
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Manuscript Number: 2008JA013040
Manuscript Title: Comment on "Geoeffectiveness of halo coronal mass ejections"
by Gopalswamy, N., S. Yashiro, and S. Akiyama"
Dear Dr. Yermolaev:
Below and/or attached are two reviews of the above manuscript. Both reviewers
find this work significant and potentially suitable for publication in the
Journal of Geophysical Research - Space Physics, but they have a number of
comments that first need to be carefully addressed.
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Thank you for choosing the Journal of Geophysical Research - Space Physics.
Sincerely,
Zuyin Pu
Editor, Journal of Geophysical Research - Space Physics
Reply to Reviewer #1
--------------------
I thank Reviewer for consideration of the manuscript and useful comments. Some
of them are accepted. However I can not agree with some remarks and would like
to explain my point of view and make several comments (see below). I marked my
comments by YY.
Review of "Comment on "Geoeffectiveness of halo coronal mass ejections" by
Gopalswamy, N., S. Yashiro, and S. Akiyama"" by Yuri Yermolaev [Comment
MS#2008JA013040] and Reply by Gopalswamy, N., S. Yashiro, and S. Akiyama

This exchange continues a series of papers and comments on other papers by
Yermolaev on the topic of halo CMEs and their geoeffectiveness in causing
geomagnetic storms. In his short comment, he criticizes Gopalswamy et al. for 1)
not contrasting their high geoeffectiveness rate of halo CMEs with the lower
rates of some other published results, including Yermolaev's, and 2) using an
incorrect method to assemble their list of frontside halo CMEs.
At the heart of this comment is that Gopalswamy used a commonly accepted method
of identifying SOHO LASCO frontside halo CMEs, those most likely to be aimed at
Earth from SOHO's L1 position. This is to assume that any frontside CME will
have visible disk activity associated with its launch, and any halo CMEs that
are not associated with disk activity are assumed to be aimed anti-Earthward, or
on the backside. Yermolaev points out that recent studies by Zhang et al. [2007]
and Schwenn et al. [2005] found that a few major storms could not be identified
with frontside halos and, indeed, historically there have been so-called
"problem storms" for which NO frontside surface activity could be found. A wellstudied
example was the January 1997 storm which had a faint halo CME associated
with a very weak surface event (e.g., Webb et al., 1998). Cane and colleagues
have also found that some ICMEs or ejecta at Earth, even some with magnetic
clouds, could not be associated with halo CMEs at
the Sun [Cane Richardson, 2003]. Thus, Yermolaev concludes that Gopalswamy et
al.'s procedure is "incorrect" because they misidentify some frontside halos as
backside, and, therefore, their list and conclusion on geoeffectiveness are also
"incorrect".
YY. Thanks for useful reference. I included it in the list of References.
Gopalswamy et al. reply that Yermolaev failed to show any specific examples of
misidentifications from their list, and they stand by their original conclusions.
A key point is that they only use full halo CMEs and not partial halos as was
done in some of the other studies. They provide compelling evidence that, as an
active region and its associated CMEs rotate from the east limb across the disk
to the west limb, the appearance of the CMEs changes from narrow, to partial
halos to full halos, then back again. I tend to agree with Gopalswamy et al. on
all these points. As long as one is careful to state what their selection
criteria are, then one cannot label their results as "incorrect". Yermolaev has
a good point about problem events but does not provide any compelling evidence
that Gopalswamy et al. have misidentified any backside halos that were actually
frontside with no surface activity.
YY. In my comment I specified an obvious logic mistake of authors during their
interpretation of observations: an absence of observational facts of disk
activity is not a sufficient condition that “frontside halo CMEs without disc
activity” events have been excluded from the frontside list and included in the
backside list.
Does the referee agree with this statement?
Examples in papers by Zhang et al. confirm this statement.
It is important to emphasize that the method used by Gopalswamy et al. depends
on the used instruments of observations. Thus, the list of events defined by
this method depends on instruments and will vary with development of
experimental techniques.
I added a text (bold font) in the manuscript.
It is my opinion that the comment and reply can be published nearly as is,
though the editor may wish to permit Yermolaev a response to Gopalswamy et al.'s
reply. Both documents have some spelling errors.
YY. If I understand correctly I should not significantly change the text of my
comment. As for spelling errors, English is not my native language and I would
be very grateful if the Editor office could help me improve text of my
manuscript.
New Reference:

Cane, H.V. and I.G. Richardson, JGR, 108, A4, 2003.
YY. Accepted.
Sincerely yours,
Yuri Yermolaev
Reply to Reviewer #2
--------------------
I thank Reviewer for consideration of the manuscript and useful comments. Some
of them are accepted. However I can not agree with some remarks and would like
to explain my point of view and make several comments (see below). I marked our
comments by YY.
Gopalswamy et al. [2007] obtained a high rate of geoeffectiveness, 71%, for 229
"frontside halo" CMEs observed between 1996 and 2005, which is significantly
higher than the geoeffectiveness of 40% obtained by Kim et al [2005] for 305
"frontside halo" CMEs between 1997 and 2003.
Kim et al.' result is consistent with some studies [Wang et al., 2002; Yermolaev
and Yermolaev, 2003a; 2003b].
Based on significant different rate between Gopalswamy et al and those mentioned
here, the author of the comment paper thought
that Gopalswamy et al.' rate was overestimated, and the reason was "the
selection method used by Gopalwamy et al is incorrect".
YY. I made my conclusions in the manuscript not on the basis of “significant
different rate between Gopalswamy et al and those mentioned here” but on the
basis of an obvious logic mistake of authors during their interpretation of
observations: an absence of observational facts of disk activity is not a
sufficient condition that “frontside halo CMEs without disc activity” events
have been excluded from the frontside list and included in the backside list.
I added a text (bold font) in the manuscript.
As the author mentioned that Gopalswamy et al. [2007] used a "harder criteria of
event selection" because the number of "frontside halo" CMEs selected by
Gopalswamy et al. between 1996 and 2005 (10 years) was LESS than the number of
"frontside halo" CMEs selected by Kim et al. between 1997 and 2003 (7 years). It
means that the definition of "frontside halo" CMEs" used by Gopalswamy et al.
must be different from that by Kim et al.
What is the difference of the definitions between the two papers?
YY. * Sorry. The purpose of my comment was to discuss lacks of the method used by
Gopalswamy et al., instead of Kim et al.. Therefore, to discuss the content of
my comment, it is necessary to discuss a following question: Does the referee
agree with statement presented in my previous paragraph?
The author thought Gopalswamy et al. [2007] incorrectly define FRONTSIDE and
BACKSIDE halo CMEs, and thus got his three conclusions. However, if the author's
point of view was correct, both the number of CMEs and the rate of
geoeffectiveness could be changed at most 10% due to exclusion of the solar
events that generate the 10% large magnetic storms (problem storms). This kind
of change cannot be used to explain the significant difference in the CME number
and the geoeffective rate.
YY. It is not correct estimations. Zhang et al. obtained 10% of “problem storms”
for strong magnetic storms with Dst < -100 nT while Gopalswamy et al. considered
slighter storms with Dst < -50 nT which may correspond with slighter solar
events and number of such events for “problem storms” is larger in 2-3 times. In
this case Gopalswamy et al. could easily obtain 70-percent geoeffectiveness of
CMEs instead of 50-percent one.

Actually the definition of FRONTSIDE in Gopalswamy et al.
[2007] is basically the same as in Kim et al. [2005], i.e.,
those halo CMEs that have disk (or near-surface) activity associated.
YY. What is a source of this statement? Is it Reviewer’s point of view ?
See also my 2 nd reply here (marked by *).
The major difference between Gopalswamy et al. [2007]
and Kim et al. [2005] (and Wang et al., 2002; Yermolaev and Yermolaev, 2003a;
2003b) is in the definition about "HALO" CMEs. In Gopalswamy et al. [2007] the
halo CME was defined as CMEs with apparent (sky plane) width of 360 degrees, but
in Kim et al. [2005] it was defined as CMEs with apparent width greater than 120
degrees.
That is why the number of frontside halo CMEs between 1996 and 2005 being
significantly less than the number between 1997 and 2003.
YY. I should note that the method used by Gopalswamy et al. is incorrect both
for full halo CMES and for partial halo CMEs. See my 2 nd reply here (marked by
*).
The halo CMEs defined as CMEs with apparent width greater than 120 degrees may
be further classified into FULL and PARTIAL halo CMEs on the basis of apparent
widths equal to and less than 360 degrees, respectively.
Statistical studies (e.g., Zhao Webb, 2007) show that about one third of halo
CMEs are full halo CMEs, and two third are partial halo CMEs; about three fourth
of frontside full halo CMEs and one fourth of frontside partial halo CMEs have
geostorms associated. It can be calculated that the number of frontside halo
CMEs is ~687 between 1996 and 2005, and the rate of the frontside halo CMEs is
~40% using the data (71% and 229) provided in Gopalswamy et al.
YY. I could not find a paper corresponding to “Zhao Webb, 2007”. The purpose
of my comment was to discuss lacks of the method used by Gopalswamy et al..
Please explain what new to my comment the results of paper by Zhao and Webb,
2007 give.
Sincerely yours,
Yuri Yermolaev
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