|Evidence for the Formation of Faint, High Prominences in the Aftermath of Two Faint
Sara F. Martin, Helio Research, La Crescenta, CA, USA and Oddbjorn Engvold, Institute for
Theoretical Astrophysics, University of Oslo, Oslo, Norway
On 16 and 17 September 2004, changes in two unusually high prominences were recorded for
intervals of several hours in the H$\alpha line at Helio Research using a 10-inch aperture
telescope equipped with a narrow band (1/10 fwhm) filter. The high prominences, each reaching
an altitude 200,000 km, appeared above a long low-lying prominence that was well-observed
crossing the limb and had a maximum altitude of 60,000 km. The lower prominence had a
horizontal axis and barbs while the high prominence in H-alpha consisted of many strands of
nearly vertical structure but with only a few threads with mass streaming downward close to the
chromosphere. Because there were no apparent geometric properties or mass flows in common
between the high prominences and the low one, it is deduced that the high prominences were
associated with photospheric polarity reversal boundaries and filament channels that were at
least 20-33 degrees beyond the west limb and associated with a large decaying active region.
Additionally, LASCO movies revealed two faint CMEs on 14 Sep (19:12 UT) and 15 Sep (21:24
UT) evidently from the backside of the Sun and near the same position angles as the high
prominences. These events were most likely related to the polarity reversal boundaries within or
on the border of the large active region beyond the west limb. We suggest that each of the high
prominences developed in the 1-2 day aftermath of each of the successive CMEs. We further
suggest that the prominences are related to the formation of current sheets anticipated by (Lin
and Forbes 2000) or magnetic interfaces (Lin and van Ballegooijen 2001) that, in either case,
are continuing to evolve one to two days after eruptive events. Support from NSF grant
ATM-0209395 is acknowledged.
Lin and van Ballegooijen 2001, AGU, abs. SH12B-0754.
Lin and Forbes 2000 BAAS 32, p.842.
Other evidence of the formation of current sheets is provided by coaxial bright rays suddenly
observed several hours after a CME by Webb et al. (2003 JGR 108, Issue A12, pp. SSH 6-1).
http://helioresearch.org/2005Jan AAS paper: website and file name referred to in the AAS
For this paper, the running identifier is 805