42 research outputs found
Specific interplanetary conditions for CIR-, Sheath-, and ICME-induced geomagnetic storms obtained by double superposed epoch analysis
The comparison of specific interplanetary conditions for 798 magnetic storms
with Dst < -50 nT for the period 1976-2000 was made on the basis of the OMNI
archive data.We categorized various large-scale types of solar wind as
interplanetary drivers of storms: corotating interaction region (CIR), Sheath,
interplanetary CME (ICME) including magnetic cloud (MC) and Ejecta, separately
MC and Ejecta, and "Indeterminate" type. The data processing was carried out by
the method of double superposed epoch analysis which uses two reference times
(onset of storm and the minimum Dst index) and make a re-scaling of main phase
of storm a such way that after this transformation all storms have equal
durations of main phase in new time reference frame. This method reproduced
some well-known results and allowed us to obtain some new results.
Specifically, obtained results demonstrate high importance of Sheath in
generation of magnetic storms as well as a significant differences in
properties of MC and Ejecta and in their geoeffectiveness.Comment: 21 pages, 9 figures, 1 table, submitted to J. of Advances in Space
Research on 29 July, 2009 for Special Issue "Space Weather Advances
Geomagnetic storm dependence on the solar flare class
Content. Solar flares are often used as precursors of geomagnetic storms. In
particular, Howard and Tappin (2005) recently published in A&A a dependence
between X-ray class of solar flares and Ap and Dst indexes of geomagnetic
storms which contradicts to early published results.
Aims. We compare published results on flare-storm dependences and discuss
possible sources of the discrepancy.
Methods. We analyze following sources of difference: (1) different intervals
of observations, (2) different statistics and (3) different methods of event
identification and comparison.
Results. Our analysis shows that magnitude of geomagnetic storms is likely to
be independent on X-ray class of solar flares.Comment: 3 pages, 1 tabl
Comment on "CAWSES November 7-8, 2004, superstorm: Complex solar and interplanetary features in the post-solar maximum phase" by B. T. Tsurutani, E. Echer, F. L. Guarnieri, and J. U. Kozyra
Recently Tsurutani et al., (2008) (Paper 1) analyzed the complex
interplanetary structures during 7 to 8 November, 2004 to identify their
properties as well as resultant geomagnetic effects and the solar origins.
Besides mentioned paper by Gopalswamy et al., (2006) the solar and
interplanetary sources of geomagnetic storm on 7-10 November, 2004 have also
been discussed in details in series of other papers. Some conclusions of these
works essentially differ from conclusions of the Paper 1 but have not been
discussed by authors of Paper 1. In this comment we would like to discuss some
of these distinctions.Comment: Submitted for publication in Geophysical Research Letter
Comment on "Are periodic solar wind number density structures formed in the solar corona?" by N. M. Viall et al., 2009, Geophys. Res. Lett., 36, L23102, doi:10.1029/2009GL041191
Location of formation of periodic solar wind number density structures is
discussed. Observation of proton and alpha anticorrelation in these structures
[Viall et al., 2009] indicates that taking into account that bulk velocity of
aplha-particles is higher than that of proton the place of formation for these
structures should be located at distance less 0.002 AU from place of
observation.Comment: 6 pages, submitted in GR