Low-Latitude Aurorae during the Extreme Space Weather Events in 1859. (arXiv:1811.02786v1 [physics.space-ph])

Low-Latitude Aurorae during the Extreme Space Weather Events in 1859. (arXiv:1811.02786v1 [physics.space-ph])
<a href="http://arxiv.org/find/physics/1/au:+Hayakawa_H/0/1/0/all/0/1">Hisashi Hayakawa</a>, <a href="http://arxiv.org/find/physics/1/au:+Ebihara_Y/0/1/0/all/0/1">Yusuke Ebihara</a>, <a href="http://arxiv.org/find/physics/1/au:+Hand_D/0/1/0/all/0/1">David P. Hand</a>, <a href="http://arxiv.org/find/physics/1/au:+Hayakawa_S/0/1/0/all/0/1">Satoshi Hayakawa</a>, <a href="http://arxiv.org/find/physics/1/au:+Kumar_S/0/1/0/all/0/1">Sandeep Kumar</a>, <a href="http://arxiv.org/find/physics/1/au:+Mukherjee_S/0/1/0/all/0/1">Shyamoli Mukherjee</a>, <a href="http://arxiv.org/find/physics/1/au:+Veenadhari_B/0/1/0/all/0/1">B.Veenadhari</a>

The Carrington storm (September 1/2, 1859) is one of the largest magnetic
storms ever observed and it has caused global auroral displays in low-latitude
areas, together with a series of multiple magnetic storms during August 28 and
September 4, 1859. In this study, we revisit contemporary auroral observation
records to extract information on their elevation angle, color, and direction
to investigate this stormy interval in detail. We first examine their
equatorward boundary of “auroral emission with multiple colors” based on
descriptions of elevation angle and color. We find that their locations were
36.5 deg ILAT on August 28/29 and 32.7 deg ILAT on September 1/2, suggesting
that trapped electrons moved to, at least, L~1.55 and L~1.41, respectively. The
equatorward boundary of “purely red emission” was likely located at 30.8 deg
ILAT on September 1/2. If “purely red emission” was a stable auroral red arc,
it would suggest that trapped protons moved to, at least, L~1.36. This
reconstruction with observed auroral emission regions provides conservative
estimations of magnetic storm intensities. We compare the auroral records with
magnetic observations. We confirm that multiple magnetic storms occurred during
this stormy interval, and that the equatorward expansion of the auroral oval is
consistent with the timing of magnetic disturbances. It is possible that the
August 28/29 interplanetary coronal mass ejections (ICMEs) cleared out the
interplanetary medium, making the ICMEs for the Carrington storm on September
1/2 more geoeffective.

The Carrington storm (September 1/2, 1859) is one of the largest magnetic
storms ever observed and it has caused global auroral displays in low-latitude
areas, together with a series of multiple magnetic storms during August 28 and
September 4, 1859. In this study, we revisit contemporary auroral observation
records to extract information on their elevation angle, color, and direction
to investigate this stormy interval in detail. We first examine their
equatorward boundary of “auroral emission with multiple colors” based on
descriptions of elevation angle and color. We find that their locations were
36.5 deg ILAT on August 28/29 and 32.7 deg ILAT on September 1/2, suggesting
that trapped electrons moved to, at least, L~1.55 and L~1.41, respectively. The
equatorward boundary of “purely red emission” was likely located at 30.8 deg
ILAT on September 1/2. If “purely red emission” was a stable auroral red arc,
it would suggest that trapped protons moved to, at least, L~1.36. This
reconstruction with observed auroral emission regions provides conservative
estimations of magnetic storm intensities. We compare the auroral records with
magnetic observations. We confirm that multiple magnetic storms occurred during
this stormy interval, and that the equatorward expansion of the auroral oval is
consistent with the timing of magnetic disturbances. It is possible that the
August 28/29 interplanetary coronal mass ejections (ICMEs) cleared out the
interplanetary medium, making the ICMEs for the Carrington storm on September
1/2 more geoeffective.

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