A solar research team from New Jersey Institute of Technology (NJIT) has discovered new information about the sun’s surface, known as the photosphere. Haimin Wang, Ph.D., professor of physics at NJIT, who led this team, detected rapid changes last July in magnetic fields on the sun’s surface. Such rapid changes are associated with flares and coronal mass ejections (CME).
Wang will present this information June 19, 2003 during a meeting of the solar physics division of the American Astronomical Society in the applied physics laboratory of Johns Hopkins University, Baltimore, Md.
“This is good news for the researchers of space weather, because our information will enable scientists in industry and government to better understand and predict the likelihood of flares and prepare for and mitigate adverse consequences,” said Wang.
Until recently, physicists have not known much about the rapid changes of surface magnetic fields associated with flares and CMEs, which can harm activities in the earth’s atmosphere. Often, these violent eruptions spew electromagnetic radiation, energetic particles and move in mass motions. They not only disrupt space weather but also can negatively impact human activities ranging from cell phone service to space and airline flights.
Now, however, scientists have studied and photographed about a dozen flares in different active regions and observed and documented their warning signs, including times prior to eruption.
Of special interest to solar researchers has been this group’s observation on July 26, 2002, which has not yet been published. Other research by the NJIT team about this phenomenon was published last year in the June, September and December issues of The Astrophysical Journal. The new, unpublished material includes three graphs and four clear photographs, illustrating the best examples yet of their discovery.
(Attention Editors: Copies of graphs and photos are available either at the meeting or from Sheryl Weinstein, 973-596-3436.)
The NJIT team was able to see and clearly illustrate the sun’s surface before and after the July 26, 2002, flare, including the enhancement of the magnetic field. “The photo clearly shows that the enhancement of the magnetic field immediately followed the flare,” said Wang. “This is news to physicists who often believe that only the magnetic field in the higher atmosphere of the sun can change so rapidly,” said Wang.
Wang’s team captured these images with the aid of a new generation of telescopic equipment. NJIT has been a national leader in the production of such equipment. For Wang’s research, a Digital Magnetograph System, built by NJIT doctoral student Tom Spirock, aided the NJIT team. The system was located at Big Bear Solar Observatory, Big Bear, Calif., a facility managed by NJIT since 1997. This work was also supported by satellite data from NASA and research grants totaling more than a million dollars from NASA, the National Science Foundation (NSF) and the Office of Naval Research (ONR).
Scientists have known for many decades that flares and coronal mass ejections are associated with solar magnetic fields and their evolution. The scientists have previously observed the rapid changes of magnetic field structure in the atmosphere’s higher layer, the chromosphere and corona. However there had been no evidence of rapid changes of magnetic fields in the photosphere.
The NJIT team studied the problem and discovered rapid changes of surface magnetic fields in about a dozen events. The changes are associated with flares both in time and space. “The time element is important to anyone studying space weather,” noted Wang.
According to Wang, it takes anywhere from a few minutes to an hour for a magnetic field to change from a pre- to post-flare configuration. Warning signs include a sudden increase in one magnetic polarity, with new sunspots forming while other sunspots disappear or expand. The strength of the transverse field and the twist of the magnetic field line will rapidly increase, too.
Wang attributes the unusual behavior of the magnetic field lines to their inherent instability. “For each flare, the field might appear to change in one of these three different ways,” said Wang. “In one scenario, field lines might connect and form new loops. Another version might be a field line shooting out from the photosphere into the upper atmosphere. And yet a third possibility would be a U-shaped magnetic loop erupting from the photosphere.”
NASA satellite mission data used in this research included information from the Transition Region and Corona Explore (TRACE), Solar Heliospheric Observatory (SOHO) and Ramaty High Energy Solar Spectroscopic Imager (RHESSI).