NDLI: Transverse Oscillations in Coronal Loops Observed with TRACE – II. Measurements of Geometric and Physical Parameters

Content Provider	Springer Nature Link
Author	Aschwanden, Markus J. De Pontieu, Bart Schrijver, Carolus J. Title, Alan M.
Copyright Year	2002
Abstract	We measure geometric and physical parameters oftransverse oscillations in 26 coronal loops, out of the 17 events described in Paper I by Schrijver, Aschwanden, and Title (2002). These events, lasting from 7 to 90 min, have been recorded with the Transition Region and Coronal Explorer (TRACE) in the 171 and 195 Å wavelength bands with a characteristic angular resolution of 1", with time cadences of 15–75 seconds. We estimate the unprojected loop (half) length L and orientation of the loop plane, based on a best-fit of a circular geometry. Then we measure the amplitude A(t) of transverse oscillations at the loop position with the largest amplitude. We decompose the time series of the transverse loop motion into an oscillating component A $_{osc}$(t) and a slowly-varying trend A $_{trend}$(t). We find oscillation periods in the range of P=2–33 min, transverse amplitudes of A=100–8800 km, loop half lengths of L=37 000–291 000 km, and decay times of t $_{d}$=3.2–21 min. We estimate a lower limit of the loop densities to be in the range of n $_{loop}$=0.13–1.7×10$^{9}$ cm$^{−3}$. The oscillations show (1) strong deviations from periodic pulses, (2) spatially asymmetric oscillation amplitudes along the loops, and (3) nonlinear transverse motions of the centroid of the oscillation amplitude. From these properties we conclude that most of the oscillating loops do not fit the simple model of kink eigen-mode oscillations, but rather manifest flare-induced impulsively generated MHD waves, which propagate forth and back in the loops and decay quickly by wave leakage or damping. In contrast to earlier work we find that the observed damping times are compatible with estimates of wave leakage through the footpoints, for chromospheric density scale heights of ≈400–2400 km. We conclude that transverse oscillations are most likely excited in loops that (1) are located near magnetic nullpoints or separator lines, and (2) are hit by a sufficiently fast exciter. These two conditions may explain the relative rarity of detected loop oscillations. We show that coronal seismology based on measurements of oscillating loop properties is challenging due to the uncertainties in estimating various loop parameters. We find that a more accurate determination of loop densities and magnetic fields, as well as advanced numerical modeling of oscillating loops, are necessary conditions for true coronal seismology.
Starting Page	99
Ending Page	132
Page Count	34
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	206
Issue Number	1
e-ISSN	1573093X
Language	English
Publisher	Kluwer Academic Publishers
Publisher Date	2002-01-01
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Astronomy, Astrophysics and Cosmology Astronomy Extraterrestrial Physics, Space Sciences
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

Longitudinal intensity oscillations in coronal loops observed with TRACE – II. Discussion of Measured Parameters

Longitudinal intensity oscillations in coronal loops observed with TRACE – I. Overview of Measured Parameters

Transverse oscillations in coronal loops observed with TRACE – I. An Overview of Events, Movies, and a Discussion of Common Properties and Required Conditions

Inclination of large coronal loops observed by TRACE

Time Variability of EUV Brightenings in Coronal Loops Observed with TRACE

Transverse Oscillations of Coronal Loops with Slowly Changing Density

Catastrophic cooling and high-speed downflow in quiescent solar coronal loops observed with TRACE

Coronal Seismology Using Transverse Oscillations of Non-planar Coronal Loops

Erratum to: Transverse Oscillations of Coronal Loops with Slowly Changing Density

Transverse Oscillations in Coronal Loops Observed with TRACE – II. Measurements of Geometric and Physical Parameters

Similar Documents

Longitudinal intensity oscillations in coronal loops observed with TRACE – II. Discussion of Measured Parameters

Longitudinal intensity oscillations in coronal loops observed with TRACE – I. Overview of Measured Parameters

Transverse oscillations in coronal loops observed with TRACE – I. An Overview of Events, Movies, and a Discussion of Common Properties and Required Conditions

Inclination of large coronal loops observed by TRACE

Time Variability of EUV Brightenings in Coronal Loops Observed with TRACE

Transverse Oscillations of Coronal Loops with Slowly Changing Density

Catastrophic cooling and high-speed downflow in quiescent solar coronal loops observed with TRACE

Coronal Seismology Using Transverse Oscillations of Non-planar Coronal Loops

Erratum to: Transverse Oscillations of Coronal Loops with Slowly Changing Density

Transverse Oscillations in Coronal Loops Observed with TRACE – II. Measurements of Geometric and Physical Parameters