Good Solar Weather Site Options

[Palomar]

*I like spaceweather.com and check it at least twice during the day. Most folks here are probably familiar with it. The site hosts current sunspot count, CME updates/animations, solar wind info, animations of sunspot development, photos of solar prominences and etc.

This folder has potential. I'm quite the Sol watcher.

[ljk4-1]

Astrophysics, abstract
astro-ph/0511006

From: Takeru Ken Suzuki [view email]

Date (v1): Mon, 31 Oct 2005 22:06:59 GMT (652kb)
Date (revised v2): Thu, 24 Nov 2005 07:01:53 GMT (599kb)
Date (revised v3): Thu, 1 Dec 2005 05:38:33 GMT (599kb)
Date (revised v4): Thu, 26 Jan 2006 13:44:21 GMT (640kb)

Solar Winds Driven by Nonlinear Low-Frequency Alfven Waves from the Photosphere : Parametric Study for Fast/Slow Winds and Disappearance of Solar Winds

Authors: Takeru K. Suzuki, Shu-ichiro Inutsuka (Kyoto University)

Comments: 27 pages, 16 figures embedded, submitted for publication in J.

Geophys. Res, revised version on Jam.26, 2006

(abridged) We investigate how the properties of the corona and solar wind in the open coronal holes depend on the properties of the magnetic fields and their footpoint motions at the surface, by perfoming 1D MHD simulations from the photosphere to 0.3 or 0.1AU. We impose low-frequency (<0.05Hz) transverse fluctuations of the field lines at the photosphere with various amplitude, spectrum, and polarization in the open flux tubes with different photospheric field strength, B, and super-radial expansion of the cross section, f_max. We find that a transonic solar wind is the universal consequence. The atmosphere is also stably heated up to >10^6K by the dissipation of the Alfven waves through compressive-wave generation and wave reflection in the case of the sufficient wave input with photospheric amplitude, <dv> > 0.7km/s. The density, and accordingly the mass flux, of solar winds show a quite sensitive dependence on <dv> because of an unstable aspect of the heating by the nonlinear Alfven waves. A case with <dv>=0.4km/s gives ~50 times smaller mass flux than the fiducial case for the fast wind with <dv>=0.7km/s; solar wind almost disappears only if <dv> becomes half. We also find that the solar wind speed has a positive correlation with B/f_max, which is consistent with recent observations. We finally show that both fast and slow solar winds can be explained by the single process, the dissipation of the low-frequency Alfven waves, with different sets of <dv> and B/f_max. Our simulations naturally explain the observed (i) anticorrelation of the solar wind speed and the coronal temperature and (ii) larger amplitude of the Alfvenic fluctuations in the fast winds. In Appendix, we also explain our implementation of the outgoing boundary condition of the MHD waves with some numerical tests.

http://arxiv.org/abs/astro-ph/0511006

[ljk4-1]

Physics, abstract
physics/0602006

From: Ramit Bhattacharyya [view email]

Date: Wed, 1 Feb 2006 12:35:11 GMT (36kb)

Solar arcades as possible minimum dissipative relaxed states

Authors: R. Bhattacharya, M. S. Janaki, B. Dasgupta, G. P. Zank

Comments: 18 pages and seven figures

Subj-class: Plasma Physics

In our work, we have proposed the arcade structures as minimum dissipative relaxed states (including both the viscous and resistive channels) pertaining to a two-fluid description of the plasma. The obtained relaxed state is non force-free in nature and appropriate to an open system with external drives. The Euler-Lagrange equations are solved in Cartesian coordinates subject to the existing photospheric boundary conditions.

The solutions are seen to support flow-containing arcade like magnetic field configurations with inherent dissipative properties that may play an important role in the coronal heating. An interesting feature observed is the generation of different types of arcades with the variation of a single parameter characterizing the relaxed state.

Also, recent observations with the LASCO coronagraph on board the SOHO spacecraft suggest that the helmet streamers originating from the sun may have an internal triple-arcade structure. The two-fluid relaxed state obtained here is also seen to support such structures.

http://arxiv.org/abs/physics/0602006

[ljk4-1]

Physics, abstract
physics/0601197

From: Yuri Yermolaev [view email]

Date: Wed, 25 Jan 2006 14:04:20 GMT (6kb)

Geomagnetic storm dependence on the solar flare class

Authors: Yu. I. Yermolaev, M. Yu. Yermolaev

Comments: 3 pages, 1 table

Subj-class: Space Physics; Plasma Physics

Content. Solar flares are often used as precursors of geomagnetic storms. In particular, Howard and Tappin (2005) recently published in A&A a dependence between X-ray class of solar flares and Ap and Dst indexes of geomagnetic storms which contradicts to early published results.

Aims. We compare published results on flare-storm dependences and discuss possible sources of the discrepancy.

Methods. We analyze following sources of difference: (1) different intervals of observations, (2) different statistics and (3) different methods of event identification and comparison.

Results. Our analysis shows that magnitude of geomagnetic storms is likely to be independent on X-ray class of solar flares.

http://arxiv.org/abs/physics/0601197

[ljk4-1]

Astrophysics, abstract
astro-ph/0602062

From: Takeru Ken Suzuki [view email]

Date: Fri, 3 Feb 2006 00:23:22 GMT (37kb)

Forecasting Solar Wind Speeds

Authors: Takeru K. Suzuki (Kyoto Univ.)

Comments: 5 pages, 2 figures embedded, ApJL, in press

By explicitly taking into account effects of Alfven waves, I derive from a simple energetics argument a fundamental relation which predicts solar wind (SW) speeds in the vicinity of the earth from physical properties on the sun. Kojima et al. recently found from their observations that a ratio of surface magnetic field strength to an expansion factor of open magnetic flux tubes is a good indicator of the SW speed. I show by using the derived relation that this nice correlation is an evidence of the Alfven wave which accelerates SW in expanding flux tubes. The observations further require that fluctuation amplitudes of magnetic field lines at the surface should be almost universal in different coronal holes, which needs to be tested by future observations.

http://arxiv.org/abs/astro-ph/0602062

[Guest_AlexBlackwell_*]

I'll say it again, ljk4-1: You are a posting machine. It seems as if any time I click on "View New Posts" I see ljk4-1 running down the right-hand side. Are you posting manually or do you have some sort of automated script? And is posting here, by any chance, your "day job"?

Thanks again, ljk4-1.

[ljk4-1]

I'll say it again, ljk4-1: You are a posting machine.  It seems as if any time I click on "View New Posts" I see ljk4-1 running down the right-hand side.  Are you posting manually or do you have some sort of automated script?  And is posting here, by any chance, your "day job"?

Thanks again, ljk4-1.

Doug, are you hiring?

You are welcome, Alex. Like you, I just know where to look and I'm a fast reader.

[ljk4-1]

Astrophysics, abstract
astro-ph/0602174

From: Huw Morgan [view email]

Date: Wed, 8 Feb 2006 00:02:38 GMT (438kb)

The Depiction of Coronal Structure in White Light Images

Authors: Huw Morgan, Shadia Rifai Habbal, Richard Woo

Comments: 10 pages, 5 figures

The very sharp decrease of density with heliocentric distance makes imaging of coronal density structures out to a few solar radii challenging. The radial gradient in brightness can be reduced using numerous image processing techniques, thus quantitative data are manipulated to provide qualitative images. Introduced in this study is a new normalizing radial graded filter (NRGF), a simple filter for removing the radial gradient to reveal coronal structure. Applied to polarized brightness observations of the corona, the NRGF produces images which are striking in their detail. Total brightness white light images include contributions from the F corona, stray light and other instrumental contributions which need to be removed as effectively as possible to properly reveal the electron corona structure. A new procedure for subtracting this background from LASCO C2 white light total brightness images is introduced. The background is created from the unpolarized component of total brightness images and is found to be remarkably time-invariant, remaining virtually unchanged over the solar cycle. By direct comparison with polarized brightness data, we show that the new background subtracting procedure is superior in depicting coronal structure accurately, particularly when used in conjunction with the NRGF. The effectiveness of the procedures is demonstrated on a series of LASCO C2 observations of a coronal mass ejection (CME).

http://arxiv.org/abs/astro-ph/0602174