NDLI: The Number of Magnetic Null Points in the Quiet Sun Corona

Content Provider	Springer Nature Link
Author	Longcope, D. W. Parnell, C. E.
Copyright Year	2008
Abstract	The coronal magnetic field above a particular photospheric region will vanish at a certain number of points, called null points. These points can be found directly in a potential field extrapolation or their density can be estimated from the Fourier spectrum of the magnetogram. The spectral estimate, in which the extrapolated field is assumed to be random and homogeneous with Gaussian statistics, is found here to be relatively accurate for quiet Sun magnetograms from SOHO’s MDI. The majority of null points occur at low altitudes, and their distribution is dictated by high wavenumbers in the Fourier spectrum. This portion of the spectrum is affected by Poisson noise, and as many as five-sixths of null points identified from a direct extrapolation can be attributed to noise. The null distribution above 1500 km is found to depend on wavelengths that are reliably measured by MDI in either its low-resolution or high-resolution mode. After correcting the spectrum to remove white noise and compensate for the modulation transfer function we find that a potential field extrapolation contains, on average, one magnetic null point, with altitude greater than 1.5 Mm, above every 322 Mm$^{2}$ patch of quiet Sun. Analysis of 562 quiet Sun magnetograms spanning the two latest solar minima shows that the null point density is relatively constant with roughly 10% day-to-day variation. At heights above 1.5 Mm, the null point density decreases approximately as the inverse cube of height. The photospheric field in the quiet Sun is well approximated as that from discrete elements with mean flux 〈\|φ\|〉=1.0×10$^{19}$ Mx distributed randomly with density n=0.007 Mm$^{−2}$.
Starting Page	51
Ending Page	75
Page Count	25
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	254
Issue Number	1
e-ISSN	1573093X
Language	English
Publisher	Springer Netherlands
Publisher Date	2008-11-04
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	MHD Sun: Corona Sun: Magnetic fields Extraterrestrial Physics, Space Sciences Meteorology/Climatology Astrophysics
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

Radiative Cooling in MHD Models of the Quiet Sun Convection Zone and Corona

The Craig – Sneyd Analytic Solutions to the Parker Problem

The Effect of Twisted Magnetic Field on the Resonant Absorption of MHD Waves in Coronal Loops

Instrumental and Observational Artifacts in Quiet Sun Magnetic Flux Cancellation Functions

Solar EUV Spectrum Calculated for Quiet Sun Conditions

The Recovery of CME-Related Dimmings and the ICME’s Enduring Magnetic Connection to the Sun

Orientation of X-Ray Bright Points in the Quiet Sun

Resolving Azimuth Ambiguity Using Vertical Nature of Solar Quiet-Sun Magnetic Fields

Slow-Mode Oscillations and Damping of Hot Solar Coronal Loops

The Number of Magnetic Null Points in the Quiet Sun Corona

Similar Documents

Radiative Cooling in MHD Models of the Quiet Sun Convection Zone and Corona

The Craig – Sneyd Analytic Solutions to the Parker Problem

The Effect of Twisted Magnetic Field on the Resonant Absorption of MHD Waves in Coronal Loops

Instrumental and Observational Artifacts in Quiet Sun Magnetic Flux Cancellation Functions

Solar EUV Spectrum Calculated for Quiet Sun Conditions

The Recovery of CME-Related Dimmings and the ICME’s Enduring Magnetic Connection to the Sun

Orientation of X-Ray Bright Points in the Quiet Sun

Resolving Azimuth Ambiguity Using Vertical Nature of Solar Quiet-Sun Magnetic Fields

Slow-Mode Oscillations and Damping of Hot Solar Coronal Loops

The Number of Magnetic Null Points in the Quiet Sun Corona