50 research outputs found
Relating magnetic reconnection to coronal heating
It is clear that the solar corona is being heated and that coronal magnetic
fields undergo reconnection all the time. Here we attempt to show that these
two facts are in fact related - i.e. coronal reconnection generates heat. This
attempt must address the fact that topological change of field lines does not
automatically generate heat. We present one case of flux emergence where we
have measured the rate of coronal magnetic reconnection and the rate of energy
dissipation in the corona. The ratio of these two, , is a current
comparable to the amount of current expected to flow along the boundary
separating the emerged flux from the pre-existing flux overlying it. We can
generalize this relation to the overall corona in quiet Sun or in active
regions. Doing so yields estimates for the contribution to corona heating from
magnetic reconnection. These estimated rates are comparable to the amount
required to maintain the corona at its observed temperature.Comment: To appear in Phil. Trans. Royal Soc.
Heating of Flare Loops With Observationally Constrained Heating Functions
We analyze high cadence high resolution observations of a C3.2 flare obtained
by AIA/SDO on August 1, 2010. The flare is a long duration event with soft
X-ray and EUV radiation lasting for over four hours. Analysis suggests that
magnetic reconnection and formation of new loops continue for more than two
hours. Furthermore, the UV 1600\AA\ observations show that each of the
individual pixels at the feet of flare loops is brightened instantaneously with
a timescale of a few minutes, and decays over a much longer timescale of more
than 30 minutes. We use these spatially resolved UV light curves during the
rise phase to construct empirical heating functions for individual flare loops,
and model heating of coronal plasmas in these loops. The total coronal
radiation of these flare loops are compared with soft X-ray and EUV radiation
fluxes measured by GOES and AIA. This study presents a method to
observationally infer heating functions in numerous flare loops that are formed
and heated sequentially by reconnection throughout the flare, and provides a
very useful constraint to coronal heating models.Comment: This paper is revise
UV and EUV Emissions at the Flare Foot-points Observed by AIA
A solar flare is composed of impulsive energy release events by magnetic
reconnection, which forms and heats flare loops. Recent studies have revealed a
two-phase evolution pattern of UV 1600\AA\ emission at the feet of these loops:
a rapid pulse lasting for a few seconds to a few minutes, followed by a gradual
decay on timescales of a few tens of minutes. Multiple band EUV observations by
AIA further reveal very similar signatures. These two phases represent
different but related signatures of an impulsive energy release in the corona.
The rapid pulse is an immediate response of the lower atmosphere to an intense
thermal conduction flux resulting from the sudden heating of the corona to high
temperatures (we rule out energetic particles due to a lack of significant hard
X-ray emission). The gradual phase is associated with the cooling of hot plasma
that has been evaporated into the corona. The observed footpoint emission is
again powered by thermal conduction (and enthalpy), but now during a period
when approximate steady state conditions are established in the loop. UV and
EUV light curves of individual pixels may therefore be separated into
contributions from two distinct physical mechanisms to shed light on the nature
of energy transport in a flare. We demonstrate this technique using
coordinated, spatially resolved observations of UV and EUV emission from the
footpoints of a C3.2 thermal flare