Consequences of spontaneous reconnection at a two-dimensional non-force-free current layer

Magnetic neutral points, where the magnitude of the magnetic field vanishes locally, are potential locations for energy conversion in the solar corona. The fact that the magnetic field is identically zero at these points suggests that for the study of current sheet formation and of any subsequent resistive dissipation phase, a finite beta plasma should be considered, rather than neglecting the plasma pressure as has often been the case in the past. The rapid dissipation of a finite current layer in non-force-free equilibrium is investigated numerically, after the sudden onset of an anomalous resistivity. The aim of this study is to determine how the energy is redistributed during the initial diffusion phase, and what is the nature of the outward transmission of information and energy. The resistivity rapidly diffuses the current at the null point. The presence of a plasma pressure allows the vast majority of the free energy to be transferred into internal energy. Most of the converted energy is used in direct heating of the surrounding plasma, and only about 3% is converted into kinetic energy, causing a perturbation in the magnetic field and the plasma which propagates away from the null at the local fast magnetoacoustic speed. The propagating pulses show a complex structure due to the highly non-uniform initial state. It is shown that this perturbation carries no net current as it propagates away from the null. The fact that, under the assumptions taken in this paper, most of the magnetic energy released in the reconnection converts internal energy of the plasma, may be highly important for the chromospheric and coronal heating problem

PROFIL WISATAWAN MUSEUM RADYA PUSTAKA SURAKARTA

Anggit Margaret, C9407031 2011. Profil Wisatawan Museum Radya Pustaka Surakarta. Program Studi Diploma III Usaha Perjalanan Wisata Fakultas Sastra Dan Seni Rupa Universitas Sebelas Maret Surakarta. Penelitian tugas akhir ini mengkaji tentang Profil Wisatawan di Museum Radya Pustaka Surakarta. Tujuan dari penelitian ini adalah untuk mengetahui dari daerah mana saja wisatawan yang berkunjung ke Museum Radya Pustaka, bagaimana ciri-ciri wisatawan yang berkunjung ke Museum Radya Pustaka serta harapan-harapan yang diinginkan wisatawan terhadap Museum Radya Pustaka. Penelitian dilakukan dengan metode kualitatif. Pengumpulan data dilakukan melalui wawancara dengan narasumber wisatawan yang berkujung di Museum Radya Pustaka Surakarta tempat penulis melakukan penelitian, serta studi pustaka dan studi dokumen guna menambah sumber data. Hasil penelitian menunjukkan bahwa (1) Sebagian besar wisatawan yang datang berasal dari Semarang sebesar 32%. (2) Mayoritas wisatawan yang berkunjung ke Museum Radya Pustaka berusia antara 17-25 tahun dan kebanyakan dari mereka adalah pelajar atau mahasiswa dengan prosentase 52%. (3) Sebagian besar wisatawan yang datang ke Museum Radya Pustaka adalah bertujuan untuk melakukan penelitian yaitu sebesar 34%. (4) Harapan wisatawan yang berkunjung terhadap kelangsungan Museum Radya Pustaka sebagian besar adalah agar ditingkatkan lagi pengelolaan dan keamanan museum, agar kejadian hilangnya benda-benda koleksi museum tidak terulang lagi dikemudian hari. Kesimpulan dari hasil penelitian ini bahwa wisatawan yang berkujung ke Museum Radya Pustaka Surakarta mayoritas berasal dari Semarang, mayoritas berusia 17-25 tahun dan kebanyakan dari mereka adalah berprofesi sebagai pelajar dan mahasiswa. Kebanyakan wisatawan yang datang bertujuan untuk melakukan penelitian, serta harapan wisatawan terhadap Museum Radya Pustaka adalah supaya lebih ditingkatkan lagi pengelolaan dan keamanan museum

Basic topological elements of coronal magnetic fields

We model the magnetic field of a coronal active region using discrete magnetic sources and look for regions of the photospheric inversion line which are tangentially touched by coronal field lines. These locations are called 'Bald Patches'. Field lines threading these bald patch regions, together with those threading any coronal null points, determine the 'Topological Skeleton' of the field. We examine the properties of these null points and bald patch regions for two, three and four magnetic sources, and study the evolution of the coronal topological skeleton as a result of moving and varying the sources. In particular, for a four-source magnetic configuration, we establish the existence of a well-defined 'separator' field line in the absence of any coronal null points. We conclude that bald patches as well as coronal nulls constitute an elemental topological feature of the coronal field: they may be significant as possible regions for coronal current sheet formation and for prominence formation.</p

Basic topological elements of coronal magnetic fields

We model the magnetic field of a coronal active region using discrete magnetic sources and look for regions of the photospheric inversion line which are tangentially touched by coronal field lines. These locations are called 'Bald Patches'. Field lines threading these bald patch regions, together with those threading any coronal null points, determine the 'Topological Skeleton' of the field. We examine the properties of these null points and bald patch regions for two, three and four magnetic sources, and study the evolution of the coronal topological skeleton as a result of moving and varying the sources. In particular, for a four-source magnetic configuration, we establish the existence of a well-defined 'separator' field line in the absence of any coronal null points. We conclude that bald patches as well as coronal nulls constitute an elemental topological feature of the coronal field: they may be significant as possible regions for coronal current sheet formation and for prominence formation.</p

A trilinear method for finding null points in a three-dimensional vector space

Null points are important locations in vector fields, such as a magnetic field. A new technique (a trilinear method for finding null points) is presented for finding null points over a large grid of points, such as those derived from a numerical experiment. The method was designed so that the null points found would agree with any fieldlines traced using the commonly used trilinear interpolation. It is split into three parts: reduction, analysis and positioning, which, when combined, provide an efficient means of locating null points to a user-defined sub-grid accuracy. We compare the results of the trilinear method with that of a method based on the Poincare index, and discuss the accuracy and limitations of both methods.Comment: 12 pages, 4 figures, submitted to Physics of Plasma