AMFStatusIndication

When the AMF is terminated, this AMF sends the AMFStatusIndication NGAP message.
Why does the AMF send this packets?

Frame 160836: 82 bytes on wire (656 bits), 82 bytes captured (656 bits) on interface -, id 0
    Interface id: 0 (-)
        Interface name: -
    Encapsulation type: Ethernet (1)
    Arrival Time: Apr 27, 2021 17:00:55.447387000 東京 (標準時)
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1619510455.447387000 seconds
    [Time delta from previous captured frame: 0.000316000 seconds]
    [Time delta from previous displayed frame: 7.172305000 seconds]
    [Time since reference or first frame: 20349.702227000 seconds]
    Frame Number: 160836
    Frame Length: 82 bytes (656 bits)
    Capture Length: 82 bytes (656 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:sctp:ngap:ngap]
Ethernet II, Src: 00:00:00_00:00:00 (00:00:00:00:00:00), Dst: 00:00:00_00:00:00 (00:00:00:00:00:00)
    Destination: 00:00:00_00:00:00 (00:00:00:00:00:00)
        Address: 00:00:00_00:00:00 (00:00:00:00:00:00)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Source: 00:00:00_00:00:00 (00:00:00:00:00:00)
        Address: 00:00:00_00:00:00 (00:00:00:00:00:00)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 127.0.0.1, Dst: 127.0.0.1
    0100 .... = Version: 4
    .... 0101 = Header Length: 20 bytes (5)
    Differentiated Services Field: 0x02 (DSCP: CS0, ECN: ECT(0))
        0000 00.. = Differentiated Services Codepoint: Default (0)
        .... ..10 = Explicit Congestion Notification: ECN-Capable Transport codepoint '10' (2)
    Total Length: 68
    Identification: 0x04f6 (1270)
    Flags: 0x4000, Don't fragment
        0... .... .... .... = Reserved bit: Not set
        .1.. .... .... .... = Don't fragment: Set
        ..0. .... .... .... = More fragments: Not set
    Fragment offset: 0
    Time to live: 64
    Protocol: SCTP (132)
    Header checksum: 0x373c [correct]
    [Header checksum status: Good]
    [Calculated Checksum: 0x373c]
    Source: 127.0.0.1
    Destination: 127.0.0.1
Stream Control Transmission Protocol, Src Port: 38412 (38412), Dst Port: 44090 (44090)
    Source port: 38412
    Destination port: 44090
    Verification tag: 0x7ceaf1da
    [Association index: 65535]
    Checksum: 0x00000000 [unverified]
    [Checksum Status: Unverified]
    DATA chunk(ordered, complete segment, TSN: 1684619727, SID: 0, SSN: 1, PPID: 60, payload length: 19 bytes)
        Chunk type: DATA (0)
            0... .... = Bit: Stop processing of the packet
            .0.. .... = Bit: Do not report
        Chunk flags: 0x03
            .... 0... = I-Bit: Possibly delay SACK
            .... .0.. = U-Bit: Ordered delivery
            .... ..1. = B-Bit: First segment
            .... ...1 = E-Bit: Last segment
        Chunk length: 35
        Transmission sequence number: 1684619727
            [This TSN was retransmitted 1 time]
                [This TSN was retransmitted in frame 160857 (0.101608000 seconds after this frame)]
            [This chunk is acked in frame: 160858]
                [The RTT to SACK was: 0.101640000 seconds]
        Stream identifier: 0x0000
        Stream sequence number: 1
        Payload protocol identifier: NGAP (60)
        Chunk padding: 00
NG Application Protocol
    NGAP-PDU: initiatingMessage (0)
        initiatingMessage
            procedureCode: id-AMFStatusIndication (1)
            criticality: ignore (1)
            value
                AMFStatusIndication
                    protocolIEs: 1 item
                        Item 0: id-UnavailableGUAMIList
                            ProtocolIE-Field
                                id: id-UnavailableGUAMIList (120)
                                criticality: reject (0)
                                value
                                    UnavailableGUAMIList: 1 item
                                        Item 0
                                            UnavailableGUAMIItem
                                                gUAMI
                                                    pLMNIdentity: 02f839
                                                        Mobile Country Code (MCC): France (208)
                                                        Mobile Network Code (MNC): Thales communications & Security (93)
                                                    aMFRegionID: ca [bit length 8, 1100 1010 decimal value 202]
                                                    aMFSetID: fe00 [bit length 10, 6 LSB pad bits, 1111 1110  00.. .... decimal value 1016]
                                                    aMFPointer: 00 [bit length 6, 2 LSB pad bits, 0000 00.. decimal value 0]

Since AMF shall let NG-RAN know the GUAMI(s) will be unavailable and perform AMF reselection procedure.

The details are defined in TS 38.413 section 8.7.6.