ACTIVITY OF STRONGLY MAGNETIZED NEUTRON STARS

THIS PROPOSAL IS THE CONTINUATION OF A PREVIOUS 3-YEAR PROJECT THAT FOCUSED ON MODELING THE NONTHERMAL EMISSION FROM MAGNETARS AND PULSARS AND TESTING THE MODELS AGAINST NEW OBSERVATIONS IN PARTICULAR BY NUSTAR. THE PROPOSED PROJECT DEVELOPS IN TWO DIRECTIONS: (1) FIRST-PRINCIPLE SIMULATIONS OF THE MAGNETOSPHERIC ELECTRON-POSITRON DISCHARGE USING OUR CODE APERTURE (BASED ON THE PARTICLE-IN-CELL METHOD) WHICH IS SPECIFICALLY DESIGNED FOR THIS PURPOSE. ITS PERFORMANCE IS DEMONSTRATED BY THE FIRST APPLICATION TO ROTATION-POWERED PULSARS AND IT CAN SIGNIFICANTLY ADVANCE OUR UNDERSTANDING OF THE MAGNETOSPHERIC ACTIVITY OF MAGNETARS ANDPULSARS. OUR SIMULATIONS INVOLVE A DETAILED IMPLEMENTATION OF RADIATIVE PROCESSES TRACKING THE EMISSION AND PROPAGATION OF GAMMARAYS AND PRODUCTION OF ELECTRON-POSITRON PAIRS. THE RESULTS WILL PROVIDE NEW THEORETICAL FOUNDATION FOR INTERPRETING EMISSION FROM THE TWISTED MAGNETOSPHERES OF NEUTRON STARS. THEY WILL CLARIFY IN PARTICULAR THE RADIATIVE MECHANISM OF MAGNETAR BURSTS ANDPERSISTENT EMISSION. (2) INVESTIGATION OF MAGNETIC FIELD EVOLUTION INSIDE NEUTRON STARS WHICH IS ULTIMATELY RESPONSIBLE FOR DRIVING THE MAGNETOSPHERIC ACTIVITY OF MAGNETARS AND THEIR SURFACE HEATING. OUR RECENT RESULTS SUGGEST TWO NOVEL PHENOMENA IN THE SOLID CRUST OF AN ACTIVE MAGNETAR: THERMOPLASTIC WAVES AND HALL-MEDIATED AVALANCHES. WE PROPOSE TO INVESTIGATE SCENARIOS FOR THE GLOBAL MAGNETIC FIELD EVOLUTION IN THE CORE AND THE CRUST AND ITS OBSERVABLES INCLUDING (A) TWISTING OF THE EXTERNAL MAGNETOSPHERE AND THE RESULTING NONTHERMAL ACTIVITY (B) SUBSURFACE HEATING AND (C) SUDDEN CHANGES OF THE ROTATION RATE. WE WILL USE OUR MODELS AND THE RICH ACCUMULATED DATA TO DISENTANGLE THE KEY DYNAMIC PROCESSES INSIDE MAGNETARS. THIS ANALYSIS CAN CONSTRAIN THE MAGNETIC FIELDS HIDDENINSIDE MAGNETARS THE STATE OF THEIR CORE MATTER AND ITS POSSIBLE SUPERFLUIDITY.