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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0041

A search for the roots of Parker's nanoflares using Hinode

plan term

2007/10/22-2007/10/28 (a few hours in this period)

@ @


 name : P. G. Judge, A. G. de Wijn @  e-mail : pgjudge[at]comcast.net

contact person in HINODE team

 name : T. Berger @  e-mail : berger[at]lmsal.com

 abstract of observational proposal
Science justification

In 1972, Parker studied the implications of convective, turbulent
motions on the magnetic fields extending into the solar
atmosphere.  He proved that for all but highly contrived motions,
there is no mechanical equilibrium.  The magnetic fields extending
above the photosphere must evolve to dissipate the injected
electromagnetic energy on dynamical (Alfvenic) time scales.  He
dubbed this state of affairs "topological dissipation". It is
topological in nature because equilibrium places strict topological
constraints on the magnetic field, which are extremely unlikely to
be met on the Sun.  Dissipation is required to account for the
observation that most coronal and chromospheric structures live
longer than the Alfvenic crossing time.  In his 1994 monograph,
Parker showed that current sheets are a natural, spontaneous
consequence of enforcing the constraint of magnetostatic
equilibrium in forced, natural systems.  Current sheets are a
natural site for dissipation of magnetic free energy stored in the

In 1988, Parker estimated what the release of energy stored in this
way might look like, as applied to plage regions of the Sun.  His
paper was motivated by space-based observations of variability on
short time scales over the chromospheric network, which he ascribed
to the "nanoflare", a burst of heating of 10^24 erg or so. One of
the primary limitations at that time was lack of knowledge of the
surface magnetic fields, they being below the seeing limited
capability of ground-based telescopes, and limited by the short
duration of time series needed to study the evolution of the
"drivers" of the magnetic fields.  In Parker's 1988 paper, he

   "It is unfortunate that the motions of the magnetic fibrils are
   not presently available from observation, since it is the
   jiggling and wandering of those fibrils that provides most if
   the energy input to the X-ray corona. We shall assume, for the
   sake of discussion, that in keeping with the granule motions of
   1-2 km/s, the foot points of the magnetic field are shuffled
   about at random with a characteristic velocity v of the order
   of 0.5 km/s, and with a correlation length l comparable to a
   granule radius.  Hopefully, within the next decade a proper
   observational determination of v and l will become available."

In this proposal, we wish to use Hinode to obtain seeing-free time
series of duration sufficient to investigate foot point motions in
the photosphere.  We wish to study the topological forcing of the
overlying atmosphere by tracking magnetic features, the
modification of this topology throughout the chromosphere, and any
associated dissipation in the corona.

It is important for us to include the chromosphere in this study for
several reasons.  The plasma beta=1 surfaces occur somewhere in the
chromosphere. The twist/ braiding proposed by Parker may not survive
to coronal levels, more recent work has indicated that the Maxwell
stresses are large only near the "boundaries" (photosphere) of the
overlying magnetic structure, and that the magnetic fields may be
relatively uniform in the bulk of structure, including the corona
(e.g., Sakurai & Levine 1981, Arendt & Schindler 1988).

 request to SOT
The prime observing tool will be the spectro-polarimeter observing
Fe I 630.2 nm in fast raster mode.  Supporting observations from
Hinode must include

 1. H alpha observations with the NFI close to the line core.  H
 alpha data are needed to study any changes in field morphology on
 fine scales from the photosphere before reaching the corona.

 2. Ca II and/or G-band data from BFI,

 3. XRT images and EIS spectral data.

Plage, quiet Sun are required targets, near to disk center.
Coronal holes would also be of interest, if available.

The SP should be run in "fast map" mode and should capture several
supergranular cells along the slit.  A scan of 16" in E-W at 0.32"
sampling and 3.2s exposure per sample yields a cadence of 180s.
The BFI and NFI FOV can be limited to the area scanned by the SP.
The image should of course be positioned on the CCD such that it is
minimally affected by the bubbles in NFI.  A high cadence of 10-15s
is desired.  These filtergram data will aid in the interpretation
of the slower-cadence, but high-sensitivity SP data.  The G-band
and Ca data will be particularly useful in this regard.

 request to XRT
The XRT should be run to acquire images over a larger area than the
16"x164" FOV of the SP in order to capture the magnetic connections
between the area observed by SP and the neighboring structures.  The
thin Be filter would allow observations over plage, the thin Al/Poly
filter would be suitable for quiet Sun, based on data at

 request to EIS
The EIS should observe, say, a 32"x256" SP field of view in raster
mode with a narrow slit, to permit observations of line broadening
associated with the dynamics of (micro-) nano- flares. The broader
region should suffice to capture any related activity in the
corona/transition region not directly over the SP FOV.  With a 2"
slit, 16 rasters of 10 sec duration should suffice to produce enough
counts in the He II, Fe XII EIS required lines.  It would also be of
interest to include some of Peter Young's weaker lines from the upper
transition region, telemetry permitting, selected from Mg V 276.54, Mg
VI 268.99, Mg VII 278.44/280.74 and Si VII 275.35.
Since we are looking for the development of bright emission against a
weaker background, the lower count rates may be sufficient for our
purposes.  No existing study seems to match our specific goals, so new
rasters would have to be built.  As an alternative the wide 40" slit
might be used to sit and stare, but with obvious loss of line profile

 other participating instruments

Some hours for HOP41 will be scheduled in the week 43 (10/22-10/28)

A duration much longer than the evolution of individual granules will
enhance greatly the statistics of the dataset, owing to the restricted
FOV (16" x 164") of the SP proposed here, imposed by the needed
cadence.  The presence of meso-scale evolution on time scales of
several hours might be of interest, thus a duration of several hours
is requested.

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