Flare Imaging Observations
by
 the Nobeyama Radioheliograph

	Kiyoto Shibasaki
	Nobeyama Radio Observatory

Contents

	Nobeyama Radioheliograph
	Sun at 17 GHz
	Flare Images
		Geometry
		Dynamics (Thermal / Non-thermal, Oscillation)
	A New Solar Flare Scenario
		High-beta disruption (Ballooning instability)
	FASR requirements

Nobeyama Radioheliograph (NoRH)

Nobeyama Radioheliograph
(Solar Dedicated Radio Interferometer)

	Freq: 17/34 GHz (since 1992/ 1995)
	Pol:
	R/L (17 GHz)
	FOV: Full Sun
	Space Res:
	10 (5) arc sec
	Time Res:
	1 (0.1) sec
	Obs. Time:
	23 – 07 UT

Slide 5

SUN at 17 GHz

	Quiet Sun
		Polar Brightening (activity minimum)
	Active Region
		Gyroresonance Source (3rd, 2000G, 3-min Osc.)
		Coronal/Chromospheric Magnetic Field
	Prominence/Dark Filament
		Filament Eruption
	Flare
		Thermal Plasma ( f-f: Tb ~ EM/√T, gyroresonance)
		Non-thermal Electron

Flare Geometry

	Double loop configuration
	(small + large loop, parallel configuration)
		Nishio et al. (ApJ. 1997)
		Hanaoka (Solar Phys. 1997)
	Loop-loop interaction (reconnection?)
	or injection from small loop to large loop?

Slide 8

Flare Dynamics (Thermal)

Slide 10

Slide 11

Slide 12

Slide 13

Slide 14

Slide 15

Slide 16

Slide 17

Spectral Analysis of Flux Variation

	Cause of time variability
		Elementary flare bursts (de Jager)
		Sub-second structures à magnetic islands in current sheet
		Current-loop coalescence (Sakai)
		LRC-circuit (Zaitsev)
	Quasi-periodic intensity oscillation
		à Quasi-periodic acceleration  or modulation by loop oscillation

Windowed Fourier Analysis

Flare Scenario

	Low-beta scenario
		Magnetic energy (current) dominate
		Dissipation by reconnection
	High-beta scenario
		Thermal energy (and flow energy)
		~ Magnetic energy
		High-beta disruption (ballooning instability)

Magnetic Reconnection Flare Scenario

High-beta Disruption Scenario of Solar Flares  (Shibasaki, ApJ 557, 2001)

	Activities in small loops:
		Small curvature
		High density
	Flows along loops
	Activities above loops
	Injection from small loop to large loop
	Parallel magnetic field configuration
	(small, large loops)

Centrifugal force by thermal motion and bulk flow V.S. Gravity

Centrifugal Force v.s. Magnetic Tension

Equilibrium and Instability conditions

	Equilibrium at the outer surface
	βTκP +κB =
	2κc(1+βg/2‐βk)
	Instability condition
	βT＞2（lp/R）・
	（ 1+βg/2‐βk ）
	Growth time
	τ(s) ~100 √(lp9R9/T6)

Slide 26

Slide 27

Slide 28

Slide 29

Common Features in Flares and Balloons

	Turbulence (before/during the impulsive phase)
	Impulsive nature
	Loop top plasma blobs
	Plasma ejection
	Over-the-loop activity
	High-energy particle acceleration (upward and downward)
	Quasi-periodicity in particle acceleration

Further Studies for High-beta Scenario

	Beta loading mechanism (small size down to convection cell)
	Energetics
	High cadence imaging spectroscopy of loops at various temperature
	Numerical simulations of non-linearly developed ballooning instability under solar coronal condition (3-D)

FASR requirements (I)

	Emission mechanism identification
	Plasma parameters in a small loop
		Mag. field, beta, energy storage
	Dynamics in a small loop and a large loop
		Alfven transit time of the small loop
		Electron beam generation and propagation
		Relation between thermal and non-thermal el.

FASR requirements (II)

	Spatial resolution: 1” or better to resolve 10” loop structure
	Temporal resolution: 0.1 sec or better to understand dynamics
	Good image quality under high space/time resolution (wide bandwidth, good phase/amp calibration)
	High positional accuracy for fine alignment with others (e.g. SOLAR-B)
	Wide frequency coverage to identify emission mechanism and get physical parameters