Filament Facts

A spectacular pair of solar filaments has recently appeared and they have captured the attention of solar observers around the world. These filaments were imaged at 1 minute intervals using the Lunt 100 PT Ha telescope. A few hours after this movie was made, the upper filament exploded into space with a fantastic Diparation Brusque (I love that term1). Often, the filament will become activated and exhibit rapid motion prior to liftoff. This movie shows plasma movement along the filament spine. Also note the anchor points connecting the main body to the chromosphere, research shows that the direction of these anchor points are related to the filaments occurrence in the in northern or southern hemisphere.

Filaments can be classified into two general groups-those associated with active regions, and those in quiet regions. Quiet region filaments (QRF)often occur along neutral lines between magnetic areas. The second movie shows both active and quiet region filaments.

Here are some filament facts collected from the excellent book Solar Astrophysics (Foukal 2002).

Active region filaments (ARF) are narrow and low, and are often not seen as prominences on the limb. Plasma flows along the filament axis, generally into a sunspot often located at one end of the filament.

QRFs can be long and high, and can take a hedgerow shape. They are often inclined 25 degrees to the chromoshere/disc. QRF plasma in is much cooler than the surrounding corona at the same height. “Studies on line widths indicate substantial turbulence near the top of the structure,” (p324).

Typical filament plasma density 10 ¹² x cm³.

Magnetic strength: 5-10 G in QRFs. Measurement of low lying ARFs have not been made, but up to 200 G during explosions has been observed.

Temperature: 12000 F

AR1726 On the Limb and Emerging Flux Region on the Disc

This animation was made at 70 second intervals with the Lunt 100 on 26 April 2013 from 1840-1929 UT. It shows AR 1726 on the solar limb as it rotates out of view. The massive sunspot put on a spectacular display during the month of April. The movie displays modest activity at 0.7 angstroms. The exposure was set to capture limb details without washing out the disc, and results did not record faint prominence activity. The SDO movie shows quite a bit of action that was not recorded in the Ha movie. But the AR can be seen as a malstrom of boiling hot plasma with the lunt 100, and it waves goodbye with a fine display. 

A movie showing an emerging flux region near the center of the disc and it shows action typical of an emerging magnetic flux tube poking through the solar atmosphere, and an arc filament system has developed. The disc movie was made at 70 second intervals with the Lunt 100 on 26 April from 1958-2049

Here is the magnetogram from the SDO website on 26 Apr 2013, showing the polarity of the flux region

More Lunt 100 Solar Movies

These movies were made with the Lunt 100.

Motion in a Solar Filament

This solar filament was captured at 1 minute intervals on November  22, 2012. The single stacked, 0.7 ang Lunt 100 delivered a rich, detailed view of motion within the filament, with plasma moving along thin flux bundles. Filament anchor points are also evident.

Plasma Outflow from the Penumbral Edge

This movie was made at 1 minute intervals on 13 Nov 2012. It shows AR1609/1610. It shows plasma outflow from the edge of a sunspot penumbra.Plasma flow near sunspots and active regions can be very complex, with inflow and outflow occurring at the same time in  multiple areas. The movie was made with a Cemax Barlow screwed into the end of the DMK. I normally use a Televue Powermate 2.5x, but seeing was poor, so backing off on the FL produced frames that were less mushy

AR 1618, A Very Active Region

This movie shows AR1618 captured at 1 minute intervals on 21 Nov 2012 from 2009-2218 UT. The plasma within active region filaments and fibrils is moving at high speed. Several small subflares pop, as well as a small C class flare. Plasma inside solar filaments can move at speeds
of 40 miles per second.

AR mag fields indicate AR1618 is classed as a Delta magnetic field that has the potential to erupt with awesome power.

Hydrogen alpha Solar Prominence Movie

This large prominence was visible on the western solar limb on 6 Nov 2012. The feature was captured at 1 minute intervals using a Lunt 100T Ha solar telescope from 1813-1936 UT. A huge cloud of plasma suspended in the corona shows helical plasma motion as well as faint, thread-like bundles of flux tubes that connect the large plasma cloud to the chromoshere. These threads appear to be aligned with the local magnetic field and do not show helical motion, but show plasma flowing downward from the cloud. It is interesting to note that the neutral line, or polarity inversion line, is really an area of mixed polarity. Prominences have weak magnetic fields of only 3-15 Gauss and several models for prominence magnetic fields exist. Typically, temperatures in a prominence/filament range from 8500-14000 F. Plasma can race around at 3 miles per second

These 2 papers summarizes our current understanding of solar prominences and provides several models for thier structure and movement. They makes great reading on a cloudy day and can be found with a simple internet search

Physics of Solar Prominences: II – Magnetic Structure and Dynamics by D.H. Mackay,· J.T. Karpen · J.L.Ballester · B. Schmieder · G. Aulanier

New perspectives on Solar prominences by B Schmieder

A Very Long Neutral Line Filament

This spectacular neutral line filament was captured at 1 minute intervals on 28 Oct 2012 from 1810-1910 UT with a Lunt 100T. The giff shows the SDO magnetogram overlaid on the GONG Ha for 28 Oct. Note how the filament snakes its way along a magnetic inversion line that stretches to the limb and is visible in emission as a prominence. A small subflare can be seen as it erupts and displaces plasma along the line, which quickly reforms. This movie also provides an interesting view of the feature. The area closer to the center of the solar disc appears quite dark and dense, and near/on the limb the feature appears diffuse. This is due our view looking down the filament near the center of the disc, and through the filament profile as it appears on /near the limb. The movie was made to expose the disc and the plasma on the limb is very faint, but is quite visible in the lower left quadrant of the disc in the Ha-magnetogram giff (please click on the image to download the giff files if they do not open automaticaly after a moment).

AR 1585 on the Solar Limb

 

This short movie was made from 2020-2110 UT on 3 October 2012. It shows AR1585 shortly after it rotated into view. The area of plage shows a modest amount of activity, with boiling plasma and fibrils. The sunspot exhibits quite a bit of plasma flow. This movie was made at 1 minute intervals with the Lunt 100 and a DMK 21AU04 operated with Lucam Recorder.

Although it requires more processing than longer interval movies, I prefer a 1 minute interval for solar features because it creates a nice, smooth movie. Frames with poor alignment or mushy from poor seeing can be dropped from the final movie without a noticeable skip (provided not too many frames are removed). On occasion I will use a 2 minute interval for long duration events

Magnetic Fields in AR1560

 

Active Region 11560 has morphed into the most prominent magnetic feature facing earth on the solar disc. A comparison with observations made on 2 Sept 2012 reveal interesting changes. The small pores in the center area have joined together to create a giant area of magnitisim. A magnetogram dated 2 Sept shows an increase in magnetism with a large dark core. The lower right portion also shows change with less plasma flow, and increased elongation of a dark area. The magnetogram shows the elongation of the mag field as well. Magnetic activity seems to be consolidating on the lower spot, the same area that exhibited massive plasma flow 24 hours earlier. But note how subflares occur in the same area just left from the lower spot.

Most sunspot magnetic fields have a strength of  2000-3000 Gauss. How powerful is that? For reference, a typical stereo speaker magnet measures 10,000-24,000, much higher than a typical sunspot (interesting fact: it takes 160k Gauss to levitate a frog). Recent research shows field lines protrude from the dark sunspot cores